Symetrix 421m User manual

421m
421m AGC-Leveler
Users Guide

i
Table of Contents
421m
Chapter 1 Introduction 1
Chapter 2 Operator Safety Summary 2
Chapter 3 Front & Rear Panel Overview 3
Chapter 4 Installation
Chapter 5 Operation 8
Chapter 6 Applications 10
Chapter 7 Specifications 13
Chapter 8 Troubleshooting 14
Chapter 9 Warranty and Service 15
Appendix A Declaration of Conformity 17
© April 2000-01 Symetrix, Inc. All rights reserved.
Symetrix Part Number 53421M0C00
The information in this guide is subject to change without
notice. Symetrix, Inc. shall not be liable for technical or
editorial errors or omissions contained herein; nor is it liable
for incidental or consequential damages resulting from the
furnishing, performance, or use of this material.
Mention of third-party products is for informational pur-
poses only and constitutes neither an endorsement nor a
recommendation. Symetrix assumes no responsibility with
regard to the performance or use of these products.
Under copyright laws, no part of this user guide may be
reproduced or transmitted in any form or by any means,
electronic or mechanical, without permission in writing
from Symetrix, Inc. If, however, your only means of access
is electronic, permission to print one copy is hereby granted.
6408 216th St. SW
Mountlake Terrace, WA 98043 USA
Tel [phone]
Fax [phone]
Email [email protected]

421m
1
IntroductionChapter 1
Front panel
Rear panel
The Symetrix 421m is a wide-range AGC-Leveler, a peak limiter, and a downward expander that
eatures a microphone preamp, eliminating the need or a separate outboard microphone preamp in
some applications. The 421m reduces the dynamic range o its input signal by the amount o its
ratio setting. That is, i the ratio setting is 2:1, then 40 dB o input range turns into 20 dB at the
output. A ast peak limiter puts an absolute ceiling on the output level so you know that peaks are
held to the level that you set. A downward expander reduces the gain when signal levels all too
low to process, reducing the noise buildup at low signal levels. Speech ilters allow a reduction o
reduction the bandpass o the 421m to minimize eedback or ampli ier power waste caused by
spurious out-o -band signals.
AGC-Levelers can be used anywhere that you might need to reduce the dynamic range o an audio
signal over a wide range o signal levels. Possible applications include: tape duplication (especially
cassette), driving telephone lines, driving broadcast or STL transmitters, podium or lectern micro-
phones, paging systems, unattended sound systems, and music recording.
The 421m is listed by Underwriters Laboratories Inc. (UL). Samples o this product have been
evaluated by UL and meet the applicable UL Standards or Sa ety.
We recommend that you read this manual rom cover to cover. Somewhere between the con ines o
the two covers you should ind the answers to most o your questions. I not, please eel ree to
contact our Customer Service department via phone, ax, or e-mail or answers to your questions.
The numbers are:
Telephone:[phone]
Fax:[phone]
E-mail: [email protected]
Web site: www.symetrixaudio.com
RÉFÉREZ TOUTE RÉPARATION À UN TECHNICIEN QUALIFIÉ.
FABRIQUÉ AUX E.-U. PAR SYMETRIX INC., LYNNWOOD, WASHINGTON.
TYPICAL
CONNECTIONS
LYNNWOOD, WA, USA
MANUFACTURED IN
POWER
==
PIN3
XLR RING PHONE LOW(-) SIGNAL
==
XLR
PIN2 PHONE TIP SIGNAL HIGH(+)
GROUND
SIGNAL
=
SLEEVE
PHONE
=
PIN1
XLR
GND
EARTH
GND
SIG GND SIG
BALANCED/UNBALANCED LINE OUTPUT
LEVEL
TRIMTRIM
BALANCED/UNBALANCED LINE INPUT
OFF
+48V
PHANTOM
CONNECT TO
SYMETRIX 421 ONLY!
(NOT A MIDI CONNECTOR)
STEREO LINK
BALANCED MICROPHONE INPUT
LEVEL
POWER
MAXIMUM
AC INPUT
20 WATTS
+50+250-10
421m
AGC-LEVELER
OUTPUT LEVEL
SYSTEMSPEECH CURVEOUTPUT LIMITERAGC-LEVELERDOWNWARD EXPANDER (NR)
421m
AGC-LEVELER
AUTO
BYPASS
RECOVERY
AUTO-RELEASE
BYPASS
BYPASS
IN IN
125Hz 6kHz
LEVEL RATE
2:1
-54
-54 CLIP
INCREASE
DECREASE
-48 -42 -36 -30 -6-12-18-24 +12+60VU
FAST
SLOW
IN
BYPASS
ACTIVE
BYPASSSTEREO LINK
0
BYPASS
-15
THRESHOLD (Vu)
-8 +15
LIMIT
SLAVE
MASTER
EXPAND
0VU +6 [phone]-48
-45-20
BYPASS
INPUT LEVEL
IN
BYPASS
TARGET OUTPUT LEVEL
HIGH
LOW 4:1
RATIO
SLOW
FAST
RELEASETHRESHOLD (Vu)
-35

421m
2
Operator Safety Summary Chapter 2
Terms
Several notational conventions are used in this
manual. Some paragraphs may use Note, Caution,
or Warning as a heading. Certain typefaces and
capitalization are used to identify certain words.
These are:
Note Identifies information that needs
extra emphasis. A Note generally
supplies extra information to help
you to better use the 421m.
Caution Identifies information that, if not
heeded, may cause damage to the
421m or other equipment in your
system.
Warning Identifies information that, if
ignored, may be hazardous to your
health or that of others.
CAPITALS Controls, switches or other markings
on the 421m s chassis.
Boldface Strong emphasis.
Equipment Markings
AVIS:
NE PAS OUVRIR
Il ne se trouve a l’interieur aucune piece pourvant entre reparée l’usager.
SEE OWNERS MANUAL. VOIR CAHIER D’INSTRUCTIONS.
S’adresser a un reparateur compétent.
RISQUE DE CHOC ELECTRIQUE
No user serviceable parts inside. Refer servicing to qualified service personnel
.
CAUTION
WARNING:
TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE
THIS EQUIPMENT TO RAIN OR MOISTURE
DO NOT OPEN
RISK OF ELECTRIC SHOCK
The lightning flash with arrowhead symbol within an
equilateral triangle is intended to alert the user of the
presence of uninsulated dangerous voltage within
the product s enclosure that may be of sufficient
magnitude to constitute a risk of electric shock to
persons. The exclamation point within an equilateral
triangle is intended to alert the user of the presence of
important operating and maintenance (servicing)
instructions in the literature accompanying the
product (i.e. this manual).
Caution To prevent electric shock, do not use the
polarized plug supplied with the unit with
any extension cord, receptacle, or other
outlet unless the blades can be fully
inserted.
Important Safety Instructions
Please read and keep these instructions. Heed
and follow all warnings and instructions.
Install in accordance with the manufacturer s
instructions.
Power Source This product is intended to
operate from a power source that does not apply
more than 250V rms between the power supply
conductors or between either power supply
conductor and ground. A protective ground
connection, by way of the grounding conductor
in the power cord, is essential for safe operation.
Grounding The chassis of this product is
grounded through the grounding conductor of
the power cord. To avoid electric shock, plug the
power cord into a properly wired receptacle
before making any connections to the product. A
protective ground connection, by way of the
grounding conductor in the power cord, is
essential for safe operation. Do not defeat the
safetypurpose of thegrounding plug. The
grounding plug has two blades and a third
grounding prong. The third prong is provided for
your safety. When the provided plug does not fit
your outlet, consult an electrician for replacement
of the obsolete outlet.
Danger from Loss of Ground If the protective
ground connection is lost, all accessible conduc-
tive parts, including knobs and controls that may
appear to be insulated, can render an electric
shock.
Proper Power Cord Use only the power cord
and connector specified for the product and your
operating locale. Use only a cord that is in good
condition.Protectthe power cord frombeing
walked on or pinched, particularly at plugs,
convenience receptacles, and the point where
they exit from the apparatus.
Proper Fuse The user accessible fuse is a part of
the IEC AC inlet connector. The fuseholder
accepts5 x 20mm diameter fuses. For117VAC
operation, the correct value is 0.25A, 250VAC,
standard. For 230VAC operation, the correct
value is 0.125A, 250VAC, standard.
OperatingLocation Do notoperate thisequip-
mentunder anyof thefollowing conditions:
explosive atmospheres, in wet locations, in
inclement weather, improper or unknown AC
mains voltage, or if improperly fused. Do not
install near any heat source such as radiators,
heat registers, stoves, or other apparatus
(including amplifiers) that produce heat. Unplug
this apparatus during lightning storms or when
unused for long periods of time.
Stay Out of the Box To avoid personal injury (or
worse), do not remove the product covers or
panels. Do not operate the product without the
covers and panels properly installed. Only use
accessories specified by the manufacturer. Clean
only with a damp cloth.
User-serviceable parts There are no user
serviceable parts inside the 421m. In case of
failure, refer all servicing to the factory. Servicing
is required when the 421m has been damaged in
any way, such as when a power supply cord or
plug is damaged, liquid has been spilled or
objects have fallen into the apparatus, the
apparatus has been exposed to rain or moisture,
does not operate normally, or has been dropped.
AVIS:
NE PAS OUVRIR
Il ne se trouve a l’interieur aucune piece pourvant entre reparée l’usager.
SEE OWNERS MANUAL. VOIR CAHIER D’INSTRUCTIONS.
S’adresser a un reparateur compétent.
RISQUE DE CHOC ELECTRIQUE
No user serviceable parts inside. Refer servicing to qualified service personnel.
CAUTION
WARNING:
TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE
THIS EQUIPMENT TO RAIN OR MOISTURE
DO NOT OPEN
RISK OF ELECTRIC SHOCK
Operator Safety Summary Chapter 2
Terms
Several notational conventions are used in this
manual. Some paragraphs may use Note, Caution,
or Warning as a heading. Certain typefaces and
capitalization are used to identify certain words.
These are:
Note Identifies information that needs
extra emphasis. A Note generally
supplies extra information to help
you to better use the 421m.
Caution Identifies information that, if not
heeded, may cause damage to the
421m or other equipment in your
system.
Warning Identifies information that, if
ignored, may be hazardous to your
health or that of others.
CAPITALS Controls, switches or other markings
on the 421m’s chassis.
Boldface Strong emphasis.
The lightning flash with arrowhead symbol within
an equilateral triangle is intended to alert the user
of the presence of uninsulated “dangerous volt-
age” within the product’s enclosure that may be of
sufficient magnitude to constitute a risk of electric
shock to persons. The exclamation point within an
equilateral triangle is intended to alert the user of the
presence of important operating and maintenance
(servicing) instructions in the literature accom-
panying the product (i.e. this manual).
Caution
To prevent electric shock, do not use the polarized
plug supplied with the unit with any extension cord,
receptacle, or other outlet unless the blades can be
fully inserted.
Important Safety Instructions
Please read and keep these instructions. Heed
and follow all warnings and instructions.
Install in accordance with the manufacturer’s
instructions.
Power Source This product is intended to op-
erate from a power source that does not apply
more than 250V rms between the power supply
conductors or between either power supply
conductor and ground. A protective ground
connection, by way of the grounding conductor
in the power cord, is essential for safe opera-
tion.
Grounding The chassis of this product is
grounded through the grounding conductor of
the power cord. To avoid electric shock, plug
the power cord into a properly wired receptacle
before making any connections to the product.
A protective ground connection, by way of
the grounding conductor in the power cord,
is essential for safe operation. Do not defeat
the safety purpose of the grounding plug.
The grounding plug has two blades and a third
grounding prong. The third prong is provided
for your safety. When the provided plug does
not fit your outlet, consult an electrician for
replacement of the obsolete outlet.
Danger from Loss of Ground If the protec-
tive ground connection is lost, all accessible
conductive parts, including knobs and controls
that may appear to be insulated, can render an
electric shock.
Proper Power Cord Use only the power cord
and connector specified for the product and
your operating locale. Use only a cord that is
in good condition. Protect the power cord
from being walked on or pinched, particularly
at plugs, convenience receptacles, and the point
where they exit from the apparatus.
Proper Fuse The user accessible fuse is a part
of the IEC AC inlet connector. The fuseholder
accepts 5 x 20mm diameter fuses. For 117VAC
operation, the correct value is 0.25A, 250VAC,
standard. For 230VAC operation, the correct
value is 0.125A, 250VAC, standard.
Proper Microphone and Cable To prevent
hazard or damage ensure that only microphone
cables and microphones designed to IEC-268-
15A are connected.
Operating Location Do not operate this
equipment under any of the following condi-
tions: explosive atmospheres, in wet locations,
in inclement weather, improper or unknown
AC mains voltage, or if improperly fused.
Do not install near any heat source such as
radiators, heat registers, stoves, or other appa-
ratus (including amplifiers) that produce heat.
Unplug this apparatus during lightning storms
or when unused for long periods of time.
Stay Out of the Box To avoid personal injury
(or worse), do not remove the product covers
or panels. Do not operate the product without
the covers and panels properly installed. Only
use accessories specified by the manufacturer.
Clean only with a damp cloth.
User-serviceable parts There are no user
serviceable parts inside the 421m. In case
of failure, refer all servicing to the factory.
Servicing is required when the 421m has been
damaged in any way, such as when a power
supply cord or plug is damaged, liquid has
been spilled or objects have fallen into the ap-
paratus, the apparatus has been exposed to rain
or moisture, does not operate normally, or has
been dropped.

421m
3
DOWNWARD EXPANDER RELEASE control
Front & Rear Panel Overview
Chapter 3
DOWNWARD EXPANDER THRESHOLD - Determines the level below which the downward
expander operates, which reduces the gain at a 1:2 dB ratio.
At the max CCW setting o the control, the threshold setting is automatic; determined by the
setting o the AUTO-RELEASE control. In this case, the downward expander acts more like a gate
(very high ratio) NOTE: the silence detector thinks that acoustic eedback is silence!
At the max CW setting, the threshold setting is low enough that all signals are above threshold,
there ore the expander is bypassed.
DOWNWARD EXPANDER RELEASE - Determines the rate o decay or the downward expander.
EXPAND LED - Tells when the downward expander is active.
LEVELER ACTIVE LED - Indicates the leveling activity. I the LED is o , then the gain o the AGC-
Leveler is rozen at the last setting. The signal level where the gain is rozen is determined by the
AUTO-RELEASE LEVEL control.
AUTO-RELEASE LEVEL - Determines the level that the input signal must exceed to allow the AGC-
Leveler to respond. I the signal level is below this threshold (active LED OFF), then the AGC gain
is rozen and the AGC allows the signal level to all to zero. This keeps the AGC-Leveler rom
undoing ades, etc.
Another way to understand this control is to think o it in terms o the minimum signal level
required to make the AGC-Leveler try to maintain the Target Output Level. Once the signal alls
below the AUTO-RELEASE setting, the AGC-Leveler allows the signal to decrease. When the
input signal exceeds the AUTO-RELEASE setting, the AGC-Leveler once again tries to maintain
constant output level.
RECOVERY RATE - Sets the basic recovery-time. Fast or speech, slow or music or music/speech.
Fast might work or music in special applications.
RATIO - Determines the input/output ratio. This control instructs the 421m how aggressively you
want to maintain the target output level. Using a 2:1 ratio, a 2dB drop in the input level results in a
1dB drop at the 421m’s output. With a 4:1 ratio, a 4dB drop at the input is limited to a 1dB decrease
at the output. The 421m computes the additional make-up gain needed or the ratio setting and
applies it to the VCA so that the output level doesn t change with the setting o the ratio control.
TARGET LEVEL - Sets the desired output level.
This chapter provides a basic overview o the 421m by describing the input and output connec-
tions, power connection, operating controls, and ront panel LED indicators.
AGC-LEVELERDOWNWARD EXPANDER (NR)
421m
AGC-LEVELER
AUTO
RECOVERY
AUTO-RELEASE
BYPASS
LEVEL RATE
2:1
INCREASE
DECREASE
FAST
SLOW
ACTIVEEXPAND
-45-20
BYPASS
TARGET OUTPUT LEVEL
HIGH
LOW 4:1
RATIO
SLOW
FAST
RELEASETHRESHOLD (Vu)
-35
AGC AUTO-RELEASE
control
RECOVERY RATE
button
RATIO control
TARGET
OUTPUT LEVEL
LEVELER
ACTIVE LED
DOWNWARD EXPANDER
THRESHOLD control
EXPAND LED
Front panel view (left)

421m
4
Front panel view (right)
OUTPUT LIMITER THRESHOLD LED - Indicates peak limiting activity.
OUTPUT LIMITER THRESHOLD - Sets the threshold o the peak (ceiling) limiter. This works in
conjunction with the leveler s ratio and target output level controls. The 421m will not allow the
peak limiter to be set higher than the setting o the target output level control. I you think about it,
it would make no sense i you allowed peaks past the target output level.
SPEECH CURVE FILTERS - The high pass ilter (button on the le t) has a 12 dB/octave rollo and
the low pass ilter (button on the right) rolls o at 24 dB/octave.
STEREO LINK - Sets the master/slave relationship between 2 units. The normal setting is IN.
BYPASS BUTTON - This control hard-wire bypasses the 421m. I STEREO LINKED, all linked
(slave) units revert to bypass when the bypass button on the master unit is out. On any individual
slave unit that has been STEREO LINKED (STEREO LINK button OUT), this button has no e ect.
INPUT LED - This meter indicates the input signal level to the 421m. It is a VU calibrated peak
reading meter.
OUTPUT LED - This meter indicates the output signal level o the 421m. It is a VU calibrated peak
reading meter.
OUTPUT LEVEL
SYSTEMSPEECH CURVEOUTPUT LIMITER
BYPASSBYPASS
IN IN
125Hz 6kHz
-54
-54 CLIP
E
-48 -42 -36 -30 -6-12-18-24 +12+60VU
IN
BYPASS
BYPASSSTEREO LINK
0
BYPASS
-15
THRESHOLD (Vu)
-8 +15
LIMIT
SLAVE
MASTER
0VU +6 [phone]-48
INPUT LEVEL
IN
BYPASS
V
EL
OUTPUT LIMITER
THRESHOLD LED
OUTPUT LIMITER THRESHOLD control
SPEECH CURVE filters
(125 Hz high pass,
6kHz low pass)
STEREO LINK button
BYPASS button INPUT LED meter
OUTPUT LED meter

421m
5
Rear panel view (left)
SERIAL NUMBER
AC INPUT connector OUTPUT connectors
RÉFÉREZ TOUTE RÉPARATION ÀUN TECHNICIEN QUALIFIÉ.
FABRIQUÉAUX E.-U. PAR SYMETRIX INC., LYNNWOOD, WASHINGTON.
LYNNWOOD, WA, USA
MANUFACTURED IN
GND
EART
H
GND
SIG
BALANCED/UNBALANCED LINE OUTPUT
CONNECT TO
SYMETRIX 421 ONLY!
(NOT A MIDI CONNECTOR)
STEREO LINK
POWER
MAXIMUM
AC INPUT
20 WATTS
421m
AGC-LEVELER
STEREO LINK connector
AC INPUT - This connector accepts nominal AC power sources o 115 volts or 230 volts [see
Appendix A (Speci ications) or voltage tolerance ranges]. See chapter 4 (Installation) or details
on the detachable (IEC) power cable.
SERIAL NUMBER - Write this down in a sa e place (how about the ront o this user’s guide?).
STEREO LINK - This 5-pin DIN emale connector is used to link two 421m's or stereo operation.
Re er to the STEREO INTERCONNECT section on page 6 or additional in ormation.
OUTPUT CONNECTORS - These are electronically balanced, line level, low impedance outputs.
XLR pin 1 is ground, pin 2 is high, and pin 3 is low. The 1/4" connector tip is high, ring is low, and
sleeve is ground. The screw terminal output is wired in parallel to the ø" and XLR connectors.
Rear panel view (right)
LINE INPUT - These connectors are electronically balanced, line level, bridging inputs. The 1/4"
connector tip is high, ring is low, and sleeve is ground. The screw terminal input is wired in parallel
to the 1/4" connector.
MICROPHONE INPUT - This connector is a balanced, low impedance input. The emale XLR pin 2
is high, pin 3 is low, and pin 1 is ground.
MIC LEVEL TRIM - Adjusts the gain o the microphone preamp rom a minimum o 25dB to a
maximum o 50dB.
PHANTOM POWER - Applies or removes microphone phantom power at the MICROPHONE
INPUT connector.
TYPICAL
CONNECTIONS
POWER
==
PIN3
XLR RING PHONE LOW(-) SIGNAL
==
XLR
PIN2 PHONE TIP SIGNAL HIGH(+)
GROUND
SIGNAL
=
SLEEVE
PHONE
=
PIN1
XLR
GND
EARTH GND SIG LEVEL
TRIMTRIM
BALANCED/UNBALANCED LINE INPUT
OFF
+48V
PHANTOM
BALANCED MICROPHONE INPUT
LEVEL
+50+250-10
LINE INPUT
connectors MIC LEVEL TRIM
LINE INPUT
LEVEL TRIM
PHANTOM POWER button
MIC INPUT connector

421m
6
Be ore you plug the 421m into a wall socket, care ully read the in ormation in the ollowing chapter.
AC Line Connection
A sticker on the right end o the unit (as viewed rom the ront) indicates the nominal voltage
setting or the unit as it le t the Symetrix actory. I this does not correspond to the voltage setting
or your locale then do not attempt to apply power to the 421m. Instead, return the unit to your
local Symetrix distributor or modi ication or replacement.
The 421m is shipped rom the Symetrix actory with a detachable AC power cable (IEC standard)
included. Depending on the intended destination, the power plug is either the US type (intended
or 115VAC use), or the Europlug type. I the power cable’s plug is not right or your locale, then
please contact your local Symetrix distributor or the proper cable.
Once you have determined that the 421m’s operating voltage matches that o your locale and you
are ready to begin, ollow these steps:
1. Plug the socket end o the power cable into the recessed AC power receptacle on the back o
the 421m.
2. Plug the other end o the power cable into a three-hole grounded outlet or power strip.
Warning: The 421m is intended to be electrically grounded. It has been provided with a three-
wire grounding plug - a plug that has a third (grounding) pin. This plug will fit only
a grounded AC outlet. This is a safety feature. If you are unable to insert the plug
into the outlet, contact a licensed electrician to replace the outlet with a properly
grounded outlet. Do not defeat the purpose of the grounding plug!
Mounting In An Equipment Rack
The 421m occupies one rack space (1U) in a standard equipment rack with a width o 19" (48.3cm),
a depth o 6.5"(16.8cm), and a height o 1.75"(4.45cm). Allow at least 4"(10.16cm) behind the unit
or the protrusion o connectors. We recommend you take care not to mount the 421m next to
devices that emit large electromagnetic ields, such as audio power ampli iers. To do so may
compromise the noise per ormance o the 421m. The 421m has been designed to con orm to
mechanical guidelines as described in EIA Standard RS-310-C and IEC Recommendation 297.
Audio Input Connections
The 421m’s line input connections are via a standard 1/4" phone jack, and barrier terminals. The
421m’s microphone input connection is an XLR emale. For optimum system per ormance we
recommend that the 421m be connected to balanced signals. I this is not practical in your situa-
tion, then you may connect to unbalanced sources.
Audio Output Connections
The 421m’s audio output connections are via standard male XLR jack, 1/4" phone jack, and barrier
terminals located on the rear panel. For optimum system per ormance we recommend that the 421m
be connected to balanced devices. I this is not practical in your situation, then you may connect
to unbalanced devices.
Use any combination o the input and output connections. All o the input connections are
paralleled. The XLR output connector and the balanced screw terminal outputs are paralleled. The
unbalanced output is paralleled rom the + screw terminal output. The 421 wants line level signals,
such as those ound at the output o a CD player, cassette machine, mixer output, mixer channel
insert jack, etc.
Installation Chapter 4

421m
7
StereoInterconnect
To stereo-link two 421m’s, interconnect the STEREO LINK jacks ound on the rear panels o the
units using a ive-pin DIN male to DIN male patch cord (Symetrix p/n 037010). This looks like a
MIDI cable, and a MIDI cable may actually work i all ive pins are actually connected to each
other.
Note: Although the stereo-interconnect cable looks like a MIDI cable, it isn t. There is nothing
remotely resembling MIDI inside or between two 421m's. I you connect either connector
to a MIDI device, it probably won t harm anything, but it de initely won t work.
Decide which unit is the master and which unit is the slave (using orce only i absolutely neces-
sary) and set the ront panel MASTER/SLAVE switches accordingly. In stereo-mode the slave
unit s controls are disabled and only the master unit controls a ect operation. The ollowing
diagram shows how to stereo-link two 421m’s.
Note: I there is no master unit connected via the Stereo Link connectors, the slave unit (any
unit with it’s MASTER/SLAVE switch in the OUT position) remains in bypass mode,
regardless o the setting o its bypass switch.

421m
8
Operation Chapter 5
Set the ront panel controls as ollows:
Initial Setup
DOWNWARD EXPANDER THRESHOLD Bypass
DOWNWARD EXPANDER RELEASE Straight up
AGC-LEVELER AUTO-RELEASE LEVEL Straight up
RECOVERY RATE In
RATIO 4:1
TARGET OUTPUT Straight up
SPEECH CURVE (125 Hz) Out
SPEECH CURVE (6kHz) Out
Apply an input signal to the 421m. Observe the input and output meters; there should be activity.
The input meter reads the actual input signal. The output meter reads the actual output signal.
Both meters are peak responding and are calibrated in VU (0 VU = +4 dBu = 1.23V RMS).
Set the AGC-Leveler by irst adjusting the TARGET OUTPUT LEVEL control or the output level
required. Next, decrease the setting o the RATIO control until you obtain the desired amount o
dynamic range reduction. Speech tolerates higher ratios than music. Use a higher ratio (4:1) or
stronger leveling action. The di erence between the two meters shows what the 421m is doing. Re-
member that a 1:1 ratio setting amounts to BYPASS or the AGC-Leveler. Set the RECOVERY RATE
button as required by the program material (starting point: FAST = speech, SLOW = music, SLOW
= speech and music).
In sound rein orcement applications, set the AUTO-RELEASE LEVEL control to limit the pickup
range o the microphone. Lower (more CCW) settings will increase the pickup range (the level
setting is lower, there ore the AGC-Leveler will track lower level signals), and higher settings will
orce the user to be more on-mike.
In recording, broadcast or tape duplication applications, the AUTO-RELEASE LEVEL control sets
the minimum signal level that the AGC-Leveler will track. I the input signal is music with a long
ade, the AGC-Leveler interprets the ade as a decrease in signal level and raises the gain to try to
maintain the level set by the TARGET OUTPUT LEVEL control. In e ect, the AGC-Leveler un-
does the ade, which may or may not be allowable. The AUTO-RELEASE LEVEL control sets how
ar the signal level can all be ore the AGC-Leveler stops trying to raise the gain. More CCW set-
tings lower this level, which may be what you want i you re trying to recreate the long piano chord
heard at the end o the Beatles song, "A Day In The Li e".
Set the downward expander during program pauses to minimize noise buildup by adjusting the
Threshold control until the expand activity LED illuminates. Set the RELEASE control or the de-
sired release rate.
Use the AUTO position o the DOWNWARD EXPANDER THRESHOLD control or situations
where the input signal is noisy (hum, hiss, or eedback). In AUTO mode the expander tracks the
AGC-Leveler s internal auto-release monitor. When the AGC-Leveler releases, the expander begins
working at the rate set by the RELEASE control. I the input signal contains acoustic eedback, and
nothing else above the auto release hold, the auto-release monitor ignores it, which e ectively
stops the eedback be ore it has a chance to grow into something potentially damaging.
Set the OUTPUT LIMITER by adjusting the THRESHOLD control either or the absolute maximum
output level desired (as read on the threshold control s panel scale) or as indicated on the peak-re-
sponding output meter.
Set the SPEECH CURVE buttons as necessary and as required by the situation. The 125Hz button
removes ’’boominess’’ and some o the proximity e ect caused by close-talking a single-D cardioid
microphone (such as a Shure SM-58), without making voices sound thin. The 6kHz button removes
sibilance and high- requency eedback without causing telephone voice.

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9
Note: Do not use pink noise or sine-waves or setup. It simply will not work (the ARM circuitry
will think your signal is noise). Use speech or music.
Helpful Hints
Microphone Techniques
Note: The ability o the expander to discriminate between wanted and unwanted signals is partially
determined by mic technique. Be particularly care ul o high requency sounds entering the side or
rear pattern o a cardioid mic. Most cardioid mics exhibit a sharply rising o -axis response charac-
teristic at higher requencies. Check the o -axis curves in the manu acturer’s literature. I there’s
only a 3dB - 6dB di erence between the on-axis ( rontal) response and the o -axis (side) or rear re-
sponse in the 5kHz to 10 kHz region, high requency sounds will be picked up by the mic, thereby
possibly preventing the downward expander rom reducing unwanted sounds.
Use the mic’s directional pattern to keep unwanted sources as ar o -axis as possible. Do every-
thing you can to discriminate against unwanted sounds through good mic technique. The sounds
picked up by an individual mic must be primarily the sound o the desired signal or the 421m’s
downward expander won’t be able to discriminate between signal and noise.
Optimizing Control Settings
When searching or optimum control settings, here are a ew rules to ollow:
AGC-LEVELER: The FAST setting o the RECOVERY RATE button is best suited or speech sig-
nals. Use the SLOW setting or musical or noisy signals or i you want the gain changes to be as
unobtrusive as possible.
The RATIO control determines how much o the input signal’s dynamic range makes it to the out-
put. We recommend starting at 4:1, so you can clearly hear the e ect, and then reduce the ratio i
necessary.
AUTO-RELEASE LEVEL (ARL): This control determines the signal level needed to cause gain re-
lease in the AGC-Leveler. A suggested method o setting it is, with no signal present, increase the
setting o the ARL control until the green ACTIVE LED extinguishes. Then, urther increase the
control setting slightly.
For musical signals use the SLOW setting o the RECOVERY RATE button. Set the AUTO-RE-
LEASE LEVEL control so that the ACTIVE LED is extinguished during low level musical passages,
ade-outs, or moments o silence.
DOWNWARD EXPANDER: When using the AUTO setting o the downward expander, irst set
the AUTO-RELEASE LEVEL control in the AGC-Leveler section. Then use the expander’s RE-
LEASE control to prevent expander action during short pauses.
General PA System Considerations
In a public address system, it is important to ensure that eedback cannot occur when the AGC-
Leveler reaches a state o maximum gain; or instance, when the 421m is trying to boost the volume
o a very quiet voice. Avoid this by talking into the mic just loud enough or the ACTIVE LED to
light. I you hear eedback, then raise the AUTO-RELEASE LEVEL until the eedback dies. Lower-
ing the RATIO will also help. Remember: The ACTIVE LED does not have to be on constantly
while signal is present. In act, depending on your circumstances, you may elect to set the AUTO-
RELEASE LEVEL high enough to prevent the 421m rom responding to all so t voices.
Stereo ink And Bypass Switching
The STEREO LINK and BYPASS buttons interact. In stereo mode, the designated master unit
takes over all unctions or both units, including in/bypass switching.
I the STEREO LINK button is in the out position, the 421m is in slave mode which means the 421m
gets its commands via the link cable rom the master unit.
Note: I a 421m is placed in SLAVE mode and is not connected to another 421m via a linking cable,
the unit will remain in BYPASS mode regardless o the setting o its BYPASS button. I there is a master
unit connected, then the BYPASS button on the master determines the status o the slave.

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10
Applications Chapter 6
An AGC-Leveler has many applications in recording studios, auditoriums or theatres, commercial
or industrial PA systems, tape duplication systems, and broadcast. Here ollows a small sample o
applications.
Conference or Courtroom Recording
I you’re recording con erences or courtroom proceedings, you are aced with the same problem at
the lectern microphone; i.e., some people speak too so tly while others are too loud. I possible,
install a separate 421m on each microphone and eed the outputs o the 421m’s into the line inputs
o your mixer.
I separate 421m’s or each mic are not an option, then place a single 421m between the mixer output
and the input o the tape recorder.
Broadcast Telephone Line Driver
At sometime or another every broadcast engineer ends up having to send audio down a telephone
line. O course, you need to keep levels hot, but i you hit the line too hard the phone company
rowns. It’s good practice to ensure that there is a hard limit to any signal that ends up going down
a phone line. The 421m is well suited to the task o unobtrusive, yet unyielding control o audio
levels.
As a starting point, use the SLOW recovery rate, low RATIO (2:1), and a low AUTO-RELEASE
LEVEL. Set the TARGET LEVEL control or the desired average level into the line, and then dial in
enough peak limiting to keep the peaks under control. You may want to back the TARGET LEVEL
o slightly so that you don’t need as much peak limiting. Peak limiters are more inaudible i you
only limit occasional peaks.
Foreground Music
The CD changer has propelled canned music into a new era. The problem, o course, is the wide
dynamic range o CD’s coupled with the act that di erent CD’s as mastered at diverse and unpre-
dictable levels. Most CD’s simply have too much range or oreground or background music
applications. The 421m helps reduce the overall dynamic range, while retaining some semblance o
the music’s original dynamics. You can link two units together or stereo i desired.
There’s probably no need to use the downward expander in this application, so turn the THRESH-
OLD control to the BYPASS position. Set the AGC-Leveler RATIO to 2:1 and use the SLOW
recovery rate setting. Set the AUTO-RELEASE LEVEL to 9:00 o’clock or lower. Experiment with the
PEAK LIMITER threshold, and use the PEAK LIMITER only i necessary.
Americans with Disabilities Act
The American Disabilities Act (ADA) o 1990 (Public Law 101-336) a ects any o us who supply
equipment to or operate public gathering places. There are ive major aspects (Titles) to this law, all
o which have staged implementation dates.
Title I deals with employment issues, Title II deals with public services, Title III deals with public
accommodations and services operated by private entities, Title IV deals with telecommunications,
and Title V deals with miscellaneous issues. O particular interest to sound system providers or
installers is Title III, which says that many o the places where you ind sound systems must
provide assisted listening devices or persons with sensory impairment. Some o the solutions
employed are: headphone jacks at certain seats, low powered AM or FM transmitters broadcasting
to Walkman (R) type radios or to acility-supplied radios, and in rared transmission systems.
Regardless o the transmission method, these systems all require a signal o reduced dynamic
range so that the users can hear both the so test and loudest parts o a per ormance. The 421m is
ideally suited to this application. Try moderate to high ratios (2:1 and up), and long release times.
Pick an AUTO-RELEASE level that keeps the AGC action somewhat unobtrusive. Use the peak
limiter to keep the transmitter out o clipping.

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Lectern-MountedMicrophones
A common and thoroughly vexing problem is that o the ubiquitous lectern microphone. A staple
o hotels, public meeting places, courtrooms, and churches, the podium microphone gets used and
misused by one and all.
Anyone who uses a microphone has their own idea o how and where to place the microphone
(relative to their lips, o course) and how they should speak into it. Some get their cues rom TV
(which any sel -respecting audio person knows is usually wrong), and some just make it up as they
go. Some stick the mike near their navel, just like on TV (or is it that TV-news-types have their
vocal chords somewhere new?), and others try to use it or a snack. You get the idea. What this
means to you is roller-coaster audio levels. Try the 421m. It will do or a lectern or other announce
microphones what no compressor has ever done be ore: consistent audio levels with increased
reedom rom eedback.
Some hints: use moderate ratios (3:1 to 4:1) unless you want a really in your ace sound. Use
either or both o the speech ilter switches. The AUTO-RELEASE LEVEL a ects the size o the
microphone s pickup circle. More CCW settings expand the circle, allowing the 421m to raise
lower level voices more (remember, it wont keep them rom sounding distant or o -mic!). Higher
settings restrict the pickup range o the microphone, so a weak talker won t be picked up as well
unless they move-in on the microphone to cause the gain to readjust to their voice level. In noisy
environments, try a higher (more clockwise) setting. You can use the downward expander in AUTO
mode to gate the mike o when idle. Ensure that the TARGET OUTPUT LEVEL isn t high enough
to cause eedback when the AGC-Leveler has ully engaged (you can orce a release by quickly
turning the AUTO-RELEASE LEVEL control and then returning it to its ormer setting.
Live PA
Have you ever mixed live sound or someone who just can t play at the right level? They re usually
too so t when playing rhythm, and too loud when playing leads. A 421m can help you out. Connect
the 421m into the mixer s channel insert jack, use a relatively low RATIO setting, use the expander
i you need to. Remember that lower ratio settings allow or more dynamics than the higher settings
which means more di erence between so t and loud. This trick also works on microphones that are
sung into and used or announcements. The 421m keeps the announcements audible without the
worry o orgetting to bring the ader down during a song. Again, use a low RATIO setting around
2:1. I you try this on a submix, be care ul because the large number o microphones involved
makes it that much easier to push the sound system into eedback.
Mixdown
You can use the 421m during mixdown or a number o di erent things. For voiceover’s let the 421m
ride the level o the announcer, while you set the basic announcer to music-bed ratio, or, let the
421m ride the music-bed, while you ride the announcer s level. Process background vocals with
the 421m. It will keep them consistently hot, without making them sound squashed (unless that s
what you want). Try using the 421m on individual instruments as a way o keeping their level more
consistent without radically altering their timbre.
Paging Systems
Just like the poor lectern mike, paging systems su er rom the same ills. It really doesn t matter i
the audio begins li e in a telephone system, or i you have a dedicated paging mike. Every user has
their own idea o how to use the mike. You can ight them and win with the 421m AGC-Leveler.
Secondary Sound System Feeds
Many sound systems derive secondary eeds or ancillary systems that serve related areas o a
acility. In arenas or large stadiums this might be the outer concourses, PA shadow zones, conces-
sion areas, rest rooms, dressing rooms, etc. In a church it might be the lobby or cry room. In a TV
studio, it could be the IFB (interrupted oldback) system.

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Tape Duplication
Anytime you change recording media, especially between a pro essional ormat and a consumer
ormat (how about DAT to consumer cassette?), patch a 421m into the recording chain to per orm a
gentle squeeze to match the signal level to the input o the next device and peak limiting. Try 2:1
RATIO; set the TARGET OUTPUT LEVEL control or the average level that you need and use the
limiter to control the peaks.
Many churches record the Pastor s message (sermon) and make it available on tape by the end o
the service. Considering the speed with which this must occur, a 421m might be just the thing to
keep the average levels hot, while still preventing overload.
Teleconferencing
Many telecon erence users want to record the content o the con erence. O course, audio levels
are all over the map (one participant shouts, another is timid...). Try a 421m between the audio mixer
and one track o the tape machine, and another between the telephone inter ace and another track
o the tape machine. Using separate 421m’s and separate tape tracks will help i and when someone
tries to transcribe the con erence. Keeping things separate also helps negate the 421m’s tendency
to bring the telephone inter ace s leakage (trans-hybrid loss) up to the same level as the caller,
which isn t a good idea. The 421m helps by keeping the signal levels more consistent rom caller to
caller, which is a good idea.
Theatre and Auditorium Cue Systems
An auditorium cue system consists o a microphone(s) mounted in the audience area o a theatre or
auditorium that eeds an ampli ier that drives speakers located in the backstage areas o the hall.
The potential dynamic range in this application is tremendous, ranging rom an empty room to an
audience on their eet making a plea or an encore.
A 421m, in conjunction with close miking o the person calling the cues, can work wonders keeping
this sort o system under control; keeping the level high enough to be audible, and low enough to
not be annoying. The downward expander can reduce the level when the room is very quiet, to
eliminate electronic noise, yet open up i someone speaks.
Post Production
A 421m can be invaluable in post production. How about:
Use the 421m when transferring location sound tapes. I you keep the ratio low, you ll gain
consistency with a minimum loss o dynamic range.
Use multiple 421m’s to keep various mi elements audible...Try one on FX or Foley, and on dialog.
I you re creating something that will be heard in a speci ic environment, consider using a 421m to
preprocess your mix or that environment. For instance, suppose you re making a point-o -
purchase video that will heard in a noisy department store, over a semi-ordinary television set.
With your mixer or an outboard EQ, give the dialog a good dose o 2.5k to 5k presence boost to
make it cut through the noise. Then process the overall mix through the 421m with a 3:1 ratio. This
will keep the overall level hot but consistent, and the combination o presence boosting and overall
level control will make your product audible in spite o the adverse environment in which it is
represented.
Be sure to check the previous section entitled Mixdown or additional tips and hints.

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13
SpecificationsChapter 7
Connectors
Line Inputs 1/4" TRS jack and screw terminals,
20k Balanced Bridging
Mic Input XLR-female, 10k Balanced Bridging
Outputs XLR-male,screwterminals,200OhmSource
Impedance,Differentially Balanced,+23 dBmmaximumlevel
TSphone,Unbalanced,+18 dBm maximum level
Bypass Relay controlled, hard-wire bypass in power off
and bypass conditions
Sidechain TRSphone, UnbalancedSendandReceive,
1000 Ohm Source Impedance, 10k Input Impedance
Tip=Receive,Ring=Send
Downward Expander
Ratio 1:2
Threshold -50VU (bypass) to -20VU (Auto Threshold)
AttackTime 1 ms
ReleaseTime Program dependant, 0.3 - 3.5 seconds
depending on amount and duration
AGC-Leveler
Ratio 1:1 to 4:1
Auto ReleaseThreshold -70 dBu to -30 dBu
AttackTime approximately 1 ms
ReleaseTime Program dependant, 500 ms - 5 seconds
depending on amount and duration
Target Output
Range +20 dB
PeakLimiterRatio 10:1
Threshold -15VUto+23VU (bypass)
AttackTime 1 ms for 90% gain reduction
ReleaseTime 0.8 seconds
421m Architects and Engineers Specifications
TheAutomaticGain Control (AGC)shallbe a singlechannelmodel that reduces thedynamicrange of widerange,wideband audio signals,providing
peaklimiting, downwardexpansion andbandpass limitingfilters.TheAGCshalloccupyonerackspace(1U).
The AGC shall be capable of controlling audio signals ranging from -70 dBu to +24 dBu and reducing their range by an input/output ratio ranging
from1:1 to4:1.Theinput/outputratio shallbe adjustablevia afront-panelcontrol.Fast/slowresponse speedswitching shallbeprovidedto
accommodatespeech andmusic sources.Atargetoutputlevel controlshall beprovided toshift theleveloftheoutput signalover anominal ±20dB
range.The releasetime ofthe AGCshall becontrolled bythe presenceof inputsignal andthesignalsensorshallbecapableofdiscriminatingbetween
music/speechandrandom noise orpuretones. The thresholdlevelof the signalsensor shall beadjustablevia a frontpanelcontrol and thepresenceof
signalsabove thethresholdsetting shallbe indicatedvia agreenLED.
TheAGC shallalsocontainanintegral peaklimiter havingat leasta10:1ratioand adjustablethreshold level.A greenLEDindicator shallbe providedto
indicatepeaklimiteractivity.ThepeaklimiterthresholdshalldeterminetheabsolutemaximumoutputamplitudeoftheAGC-Levelerregardlessofother
conditions.
TheAGC shallalsocontain anintegraldownward expanderhaving a1:2expansion ratiowith thresholdandrelease timecontrols. Furthermore,the
downwardexpander shall becapable ofoperatingautomatically viathesignal sensorcircuitry.A greenLED indicator shallbe providedtoindicate
downwardexpandercircuitactivity.
Bandpasslimitingfilters shallbeprovidedhavingalowpasscharacteristicof24dB/octave at6kHzandahighpasscharacteristicof12dB/octave at125
Hz.Both filtersshall becapableofbeingusedindividuallyorsimultaneously.
TheAGCshall provide identicalpeakresponding input andoutputlevel meters. These metersshallbe capable ofrespondingto signals rangingfrom-
54 VU to +12 VU (-50 dBu to +16 dBu). An output clipping indicator shall be provided.
TheAGCshallprovidefacilitiesforstereo-couplingtwounitsviaashielded5-pinDINmale-to-malecable.Afrontpanelswitchshalldesignatewhichunit
isthemasterandwhichunitistheslave.
Thelinelevel inputs shallbeactive balanced bridgingdesignsterminated with 1/4"TRS female andscrewterminals. The miclevelinput shall alsobean
activebalancedbridgingdesignusingathreepinXLRfemale(AES/IECstandardwiring). Theinput circuitryshallincorporate RFIfilters.Theoutputs
shallbe activebalanced designshavingequalsourceimpedancesandterminatedwith3-pinXLR(AES/IEC standardwiring) andscrew terminals.A
separate 1/4" TRS jack shall provide an unbalanced output.
The balanced line level inputs shall accommodate +24 dBu signals without distortion, and the balanced outputs shall be capable of delivering +23
dBmintoa 600-ohm load.The mic levelinputshall accommodate +8dBusignals. There shallbeseparate gain trimcontrolsfor the micand the line
inputs and the mic input shall provide 48v phantom power.
Overallfrequencyresponse shallbe20 Hz to20kHz, ±1dB, measuredat+4 dBm output.There shall benomore than 0.02%harmonicdistortion,
measured under the following conditions: +4 dbu input, +4 dBm output, BYPASS switch out, 1000 Hz. Residual noise output shall be no greater than -
90 dBm, measured with a 20 kHz noise bandwidth.
Whentheunitisinoperative (eitherbylossofpower, orviatheBYPASSswitch),theinputsand outputsshallbewiredtogether. Thereshallbeno
transientstransmittedtotheoutputterminalsduringeitherturn-on,turn-off,orbypassoperation(unlesssomethingupstreamgeneratestransients).
AccesstotheAGC’s sidechain shall be provided viaasingle ˘" TRS female connector. Theringconnection shall be the sidechain outputandthetip
connectionshallbe the sidechainreturn.
The AGC shall be capable of operating by means of its own built-in power supply connected to 115V nominal ac (105 to 130V) 50/60 Hz (230V
nominal,210 to260V ac,50 Hzwhere applicable).The AGCshall belisted byUnderwriters LaboratoriesInc. (UL)or otherequivalent nationally
recognizedsafetytestingagency.
TheunitshallbeaSymetrixIncorporatedmodel421mAGC-Leveler.
Mic Preamp
GainRange +15 dB to +45 dB
Impedance 10kOhms
Max Input Level +8 dBu
THD+Noise(gain controlfully clockwise) -85 dBu
Phantom Power 48V (±2)
CMRR >80 dB (10 Hz - 20 kHz)
Sonics
Frequency Response 20 to 50 kHz, +4 dBm (+0, -1 dB), (+0, -3 dB mic)
Harmonic Distortion <0.05% 20 Hz to 20 kHz, +4 dBm,
30 kHz bandwidth
Typically <0.01% @ 1000 Hz
ResidualNoise -90 dBu, 20 kHz noise bandwidth,
rms responding meter
Speech Curve
Type Switch selected cutoff filters allow tailoring LF and/or HF
response for speech applications
Frequencies LF=125 Hz, 12 dB/octave; HF=6 kHz, 24 dB/octave
Input/Output Metering
Type LED Bar Graph, 12 steps + clip
Range(minto max) 66 dB
Ballistics Peak
Calibration 0 dB=0VU=+4 dBm=1.23V
Physical
Size(hwd) 1.72 x 19 x 6.25 inches,
4.37 x 48.26 x 15.875 centimeters
Shipping Weight 8 lbs (3.63kg) net
Electrical
Connector EC 3-pole
PowerRequirements 117V nominal, 107 to 125V AC,
50 to 60 Hz, 10 watts
220V AC, 50 Hz, 10 watts
Note: The maximum operating ambient temperature is
25degreesC.
421mSpecifications

421m
14
Troubleshooting Chapter 8
No output signal:
Check cables and connections.
Determine that there really is a signal coming rom the source and that it is getting to the 421m.
Veri y cables by patching input and output connections together at the unit.
Check or AC power presence.
Check input by plugging headphones hal way into the sidechain jack and listening or input
signal (this veri ies that the unit is receiving signal).
Check output by plugging headphones into output jack.
Check downward expander threshold setting; it may be too high or the current signal level.
Stuck in bypass mode:
Check setting o the STEREO LINK button. In single unit (mono) systems, on independently
operating units and on master units, the switch should be in the IN position.
No limiter action:
Check the threshold control setting. Signal levels may be too low. Don’t try to calibrate with
sine waves. Use speech or music.
Distortion:
Is the incoming signal already distorted? Listen up stream rom the 421m (or manually place
the unit in BYPASS mode) to determine that you are eeding it a clean signal.
Buzz in the output:
Check input and output connector wiring.
Check or ground loops between interconnected system equipment.
Are all system components on the same AC ground?
Noise (hiss):
Check input signal levels and input level control settings. The input may be too low in level. I
so, boost the signal rom your console or input source.
Is the input signal already noisy? Listen up stream rom the 421m to determine i you are
eeding it a clean signal.
The 421m doesn’t power up or doesn’t respond properly:
Consult a quali ied service technician or the Symetrix actory.
Note: Repeated use blowing is a sure sign o electronic distress. Unplug the unit and make
arrangements or repair.
Warning: The fuse is located internally and lethal voltages are present inside the chassis. The
fuse is not considered user-serviceable. If the fuse is blown, the 421m probably
needs repair.

421m
15
Warranty & ServiceChapter 9
Warranty
Following are the terms and limitations of the Symetrix warranty.
Symetrix, Inc. expressly warrants to the original purchaser ( Buyer ), subject to the terms and conditions set forth
below, that the roduct will be free from defects in material and workmanship as a result of normal commercial use
for eighteen (18) months from the date of shipment.
Some Symetrix products contain embedded software and may also be accompanied by control software intended to
be run on a personal computer. Said software is specifically excluded from this warranty.
Symetrix's warranty obligation is limited to the repair, replacement, or refund at Symetrix's sole discretion, of the
part or parts of the roduct which may thus prove defective in materials or workmanship within one year from date
of purchase under normal use and which our examination discloses to our satisfaction to be thus defective,
provided that Buyer gives Symetrix prompt notice of its warranty claim and satisfactory proof thereof.
Symetrix will make every reasonable effort to ensure that parts are available to support the repair of our products
under warranty. In the event that a product or component part thereof becomes obsolete, unavailable or irreparable,
Symetrix reserves the right to refund a prorated portion of the purchase price in full satisfaction of all warranty
claims.
In order to serve you better we require that the Buyer shall, prior to shipping roduct to Symetrix for warranty
service, contact Symetrix and secure a Return Authorization Number that shall be included with the returned
roduct. This will facilitate our efforts to keep track of your roduct and process your warranty repair as quickly as
possible. Buyer will prepay all freight charges to ship the roduct to Symetrix for warranty inspection and service.
This warranty is subject to Symetrix's inspection of the roduct at its facilities and, upon Symetrix's request,
satisfactory proof of purchase (dated copy of original retail dealer s invoice.)
Symetrix reserves the right to effect repairs to the product with reconditioned components/parts. roducts once
repaired under warranty will be shipped to Buyer freight prepaid by Symetrix via United arcel Service (surface) or
any similar shipper, to any location designated by buyer within the Continental United States. At Buyer's request
and expense roduct will be returned via airfreight. Outside the continental United States, repaired or replaced
products will be returned freight collect.
THIS WARRANTY IS EX RESSLY IN LIEU OF ALL OTHER WARRANTIES EX RESS OR IM LIED, ARISING
BY LAW OR OTHERWISE (INCLUDING, WITHOUT LIMITATION ANY OBLIGATIONS OF THE SELLER WITH
RES ECT TO CONSEQUENTIAL DAMAGES) INCLUDING THE WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR USE AND OF ALL OTHER OBLIGATIONS OR LIABILITIES ON OUR ART, AND WE NEITHER
ASSUME, NOR AUTHORIZE ANY OTHER ERSON TO ASSUME FOR US, ANY OTHER LIABILITY IN CON-
NECTION WITH THE SALE OF THE RODUCT. THIS WARRANTY SHALL NOT A LY TO THIS RODUCT
OR ANY ART THERE OF WHICH HAS BEEN SUBJECT TO ACCIDENT, NEGLIGENCE, ALTERATION,
ABUSE, OR MISUSE. WE MAKE NO WARRANTY WHATSOEVER IN RES ECT TO ACCESSORIES OR ARTS
NOT SU LIED BY US. THE TERM ORIGINAL URCHASER, AS USED IN THIS WARRANTY SHALL BE
DEEMED TO MEAN THAT ERSON OR COM ANY THAT ORIGINALLY URCHASED THE RODUCT.
This Symetrix product has been designed and manufactured for use in professional/industrial systems and is not
intended for other usage. This warranty only applies to Buyers using the roduct in professional/industrial systems.
With respect to others, including but not limited to consumers for personal, family, or household use, Symetrix
expressly disclaims all warranties, including but not limited to warranties of merchantability and fitness for a
particular purpose and the express warranties as otherwise provided herein.
Symetrix reserves the right to modify the design or make additions to, or improvements to, its product lines without
making similar upgrades to roduct purchased by Buyer. Symetrix does not authorize any third party, including any
dealer or sales representative, to assume any liability, effect any repairs or modifications to the roduct, or make
any additional warranties or representation regarding the roduct or roduct information on behalf of Symetrix.
Symetrix's total liability on any claim, whether in contract, tort (including negligence) or otherwise arising out of,
connected with, or resulting from the manufacture, sale, delivery, resale, repair, replacement or use of roduct will
not exceed the purchase price of the roduct or any part thereof which gives rise to the claim. In no event will
Symetrix be liable for any incidental or consequential damages including but not limited to damage for lost revenue,
cost of capital, claims of customers for service interruptions or failure to supply, and costs and expenses incurred in
connection with labor, overhead, transportation, installation or removal of products or substitute facilities or supply
houses as a result of roduct failure.
This limited warranty gives Buyer certain rights. Buyer may have additional rights under applicable law.

421m
16
Servicing the 421m
I you have determined that your 421m requires repair services and you live outside o the
United States, please contact your local Symetrix dealer or distributor or instructions on how
to obtain service. I you reside in the U.S. then proceed as ollows:
Before sending anything to Symetrix, contact our Customer Service Department or a return
authorization (RA) number. The telephone number is [phone] or email:
[email protected]
In-warranty Repairs
To get your 421m repaired under the terms o the warranty:
1. Call us or an RA number.
2. Pack the unit in its original packaging materials.
3. Include your name, address, daytime telephone number, and a brie
statement o the problem.
4. Write the RA number on the outside o the box.
5. Ship the unit to Symetrix, reight prepaid.
We do not accept freight collect shipments.
Repairs made in-warranty will cost you only one-way reight charges. We'll prepay the return
(sur ace) reight.
I you send us your product in substandard packaging, we will charge you or actory ship-
ping materials. I you don t have the actory packaging materials, please use an oversized
carton, wrap the unit in a plastic bag, and surround it with bubble-wrap. Pack the box ull o
Styro oam peanuts. Be sure there is enough clearance in the carton to protect the rack ears
(you wouldn't believe how many units are returned with bent ears). We will return the unit in
Symetrix packaging. O course, i the repair is due to operator error, parts and labor will be
charged. In any event, i there are charges or the repair costs, you will pay or the return
reight. All charges will be COD unless you have made other arrangements (prepaid, Visa or
Mastercard).
Out-of-warranty Repairs
I the warranty period has passed, you'll be billed or all necessary parts, labor, packaging
materials, and reight charges. Please remember, you must call or an RA number be ore
sending the unit to Symetrix.

421m
17
Declarationof Conformity
Declaration of Conformity
We, Symetrix Incorporated,
6408 216th St. SW, Mountlake Terrace, Washington, USA,
declare under our sole responsibility that the product:
421m AGC-Leveler
to which this declaration relates,
is in con ormity with the ollowing standards:
EN 60065
Safety requirements for mains operated electronic and related
apparatus for household and similar general use.
EN50082-1
Electromagneticcompatibility-Genericimmunitystandard
Part 1: Residential, commercial, and light industry.
The technical construction ile is maintained at:
Symetrix, Inc.
6408 216th St. SW
Mountlake Terrace, WA, 98043
USA
The authorized representative located within the European Community is:
World Marketing Associates
P.O. Box 100
St. Austell, Cornwall, PL26 6YU, U.K.
Place o issue:Mountlake Terrace, Washington, USA
Authorized signature:
Dane Butcher, President, Symetrix Incorporated.
Appendix A

421m