Algo 1825 Duet Plus User manual

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1825 Duet Plus
Installation Guide
Algo Communication Products Ltd.
www.algosolutions.com
90-00046B

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Table of Contents
Release 2 Updates - Feb. 2012 .................... 3
Quick Install for Dry Contact Ringing........... 4
About the Duet Plus...................................... 5
Mounting ............................................................ 5
Wiring................................................................. 5
Inputs and Outputs.............................................. 7
Inside Diagram.................................................... 8
Option Jumpers................................................... 9
Block Diagram .................................................. 10
Duet Plus Specifications ............................. 11
Applications................................................ 12
Dry Contact Office Ringer.................................. 12
Loud or Outdoor Dry Contact Ringer.................. 14
Loud Ringer and Paging .................................... 16
Nortel/Avaya Digital Station Set Ringer.............. 18
Visual Alerting................................................... 20
Connecting to a Paging Amplifier....................... 22
CO or FXS Port Loud Ringing ............................. 24
Multiple Speakers ...................................... 26
Application Tips & Recommendations........ 28
Warranty and Repair.................................. 30
Duet Plus Accessories ................................. 32
Related Algo Product.................................. 32

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Release 2 Updates - Feb. 2012
The 1825 Duet Plus ringer has been updated for
2012. All features of the original Duet Plus are
maintained and the same inputs and outputs are
provided. The following lists the most important
changes affecting installers:
AUDIO
INPUT
The audio input still functions as before for dry
paging input and audio detection for loud ring
with heritage Nortel telephones. However, the
input is now rated to carry DC current up to 65
mA and may be connected directly to an Avaya
IP Office FXS port for “wet” paging. Also, if the J2
shunt is not set to PAG then the amplifier is dis-
abled, except when ringing. The shunt position is
checked each time ringing is initiated. The audio
input is not intended to be connected to CO lines
or wiring leaving a building.
TEL TIP &
RING
The input from a telephone CO line or FXS port
has been moved from the internal terminal block
to an internal RJ11 jack. If the Duet Plus is used
in an application involving telephone ring detect
then a safety approved (CSA, UL, CE, A-Tick)
modular cable will be required for connection (not
supplied).
POWER
SUPPLY
The power supply provided with the Duet Plus is
now a regulated high efficiency 24V switch mode
power supply with energy level V compliance.
LED
INDICATORS
Two LEDs are now located on the PCB. A green
LED indicates power and a red LED indicates
power limiting. These are to help installers
and Algo’s support team in the event that any
troubleshooting is required. If an over-current
condition is detected then the 1825 automatically
reduces audio level to maintain current at a safe
operating level.

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Quick Install for Dry Contact
Ringing
Step 1 Mount the unit and connect power
to the 24 VDC terminals. The power
supply is usually located in the
equipment room with power and
control contacts provided through
separate pairs in the cable from the
equipment room.
Step 2 Press the test button (bottom right of
unit). The warble should be heard on
the speaker. Adjust volume and tone
to suit (bottom left of unit).
Step 3
Connect telephone system night bell
or auxiliary ring contacts to RELAY
terminals.
Step 4 If loud or outdoor ringing is required
then connect an 8 Ω speaker such as
the 1185 to the SPKR terminals. The
internal speaker may be disabled by
removing the SPK shunt (see “Inside
Diagram” on page 8).
Note that the auxiliary speaker should
not be located beyond the perimeter of
the building. No lightning protection is
provided on the SPKR outputs.
Step 5 Close cabinet and test.

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About the Duet Plus
The Duet Plus is an auxiliary ringer compatible
with most business telephone equipment and
includes an audio amplifier for ring amplification
or voice paging.
Mounting
The Duet Plus must be mounted in a dry indoor
location. Outdoor locations can be alerted with an
external water proof horn speaker such as the Algo
1185 (See “Duet Plus Accessories” on page 32.)
The Duet Plus cabinet is opened by inserting a
screwdriver into the slot near the top of the cover
and prying gently upwards while lifting the cover.
Once open, the unit can be wall mounted with
wood screws using the two slot holes in the back.
Wiring
Connections to the Duet Plus are made at the PC
Board mounted terminal strip inside the unit. In
many cases, connections will be made to only
a few of the terminals, and those connections
depend entirely on the application. The Duet
Plus can be installed so that wiring is hidden by
entering through the back of the cabinet from
a mud ring, dedicated electrical box, or wall
opening. For surface wired applications, wire can
enter from the top, bottom, or left side.
The power supply is often located in an equipment
room and wired to a Duet Plus using one pair of

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a 3 or 4 pair 24 AWG station cable. That leaves
additional pairs for dry contact closure and/or
paging audio from the telephone equipment.
Wiring to 8 Ω speakers should be low resistance
for maximum audio power. If extra wire pairs are
available, make use of them to reduce speaker
wiring resistance. When an auxiliary speaker is
used, the wiring is normally routed from a Duet
Plus directly to the speaker using the shortest
distance possible.
Refer to input and output circuit descriptions
and application examples for specific wiring
connection information.

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Inputs and Outputs
Connection I/O Description/Function
24VDC Input Power supply input. 12 to 27
volts DC, polarity insensitive.
Maximum current with internal
speaker 160 mA, with typical 8
Ω horn speaker 500 mA.
RELAY Input Trigger circuit to detect dry
contact closure for connection
to auxiliary ringing or night bell
contacts (normally open).
SPKR Output Output to loud speaker for full
power performance. Provides
both warble and amplified au-
dio. This output can be selected
at shunt J3 for high impedance
output (10 kΩ) for connection to
slave amplifiers.
AUDIO INPUT Input Balanced 600 Ω input for voice
paging or ring amplification.
Maximum 65 mA DC.
10 VAC
DETECT
Input Trigger circuit detecting foreign
voltage. Isolated input detects
3 to 30 volts DC or AC. Input
impedance approximately 4 kΩ.
RJ11
Telephone
Jack
Input Trigger circuit detecting 20
to 150 VAC 16 to 68 Hz ring
signals from CO line or PBX sta-
tion tip and ring. Input uses RJ11
jack located internally.

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Inside Diagram
CO/PBX
PAGE
VOL DET
PAG
HI
LO
DET
TONE VOL TEST
PWR
SPK
OVER-CURRENT
24V
+_
J1
J2
J3
RJ11 Telephone Jack
Green Power
LED
Red Overcurrent
LED
OFF
Fig. 1 - Inside Diagram of the Duet Plus

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Option Jumpers
J1 HI High level input paging signal
(0 to +12 dBm)
LO Low level input paging signal
(-18 to 0 dBm)
DET Maximum gain for very low input
levels. Use for audio detection ap-
plication only.
J2 DET Audio input signal routed to detection
circuit.
PAG Audio input signal routed to amplifier.
OFF Audio input disabled
(Shunt on left posts).
J3 PWR Speaker output provided directly
when shunt in. With shunt out, signal
is provided through 10 kΩ resistor.
SPK When in, connects internal speaker.
If the audio input feature is not being used, then it
is recommended that the J2 shunt be positioned on
the two left posts as shown above (for OFF). This will
provide the lowest idle speaker noise and prevent
unintentional activation of the warble. If the PAG
shunt is in the OFF position, the speaker amplifier
is disabled, except when ringing. The PAG shunt is
checked each time warble begins so if moving the
PAG shunt, press the TEST button momentarily to
update settings.

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Block Diagram
Internal
Speaker
32 OHM
Audio
Input
Relay
10VAC
T
R
Aux
SPKR
Warble
Oscillator
Tone
Vol
10k
J3
PWR
SPK Power
Amp
Ring
Detect
Low
Voltage
Detect
Dry
Contact
Detect
Audio
Detect
J2
DET
PA
G
Pre-Amp
PAG
VOL
J1 DET
HI LO
Fig. 2 - Block Diagram of the Duet Plus
All inputs (including power) are polarity insensitive.

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Duet Plus Specifications
Min Typ Max Unit
Supply Voltage 12 24 26.9 Vdc
Supply Current
(using internal speaker) 160 mA
(8 Ω load at 9 W) 500 mA
(16 Ω load at 5 W) 400 mA
Output power to auxiliary speaker (no clipping) 6.0 Watts
Dry contact closure detection
Contact and loop resistance 0 2 kΩ
Open circuit voltage 5Vdc
Loop current 110 mA
Low voltage detection circuit
Input impedance 4kΩ
DC voltage input range 330 Vdc
AC voltage input range 330 Vrms
Telephone ring detection
Ring detect voltage 20/25 Hz 20 Vrms
Input impedance 50 kΩ
Audio/Paging input
Input impedance 600 Ω
Page input level (HI) 0dBm
Page input level (LO) -18 dBm
Audio detection level - 43 +12 dBm
Output sound pressure at 1 m
Internal speaker only 93 dBA
Typical 8 Ω horn speaker 112 dBA
Output warble frequency
High tone 360 960 Hz
Low tone 290 770 Hz
Modulation 412 Hz
Operating temperature 0° 40° C
Note: Specifications are subject to change without notice.

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Applications
Dry Contact Office Ringer
This application represents the most common
application for the Duet Plus. The night bell or
auxiliary ring contacts (make and common) are
connected to the RELAY terminals of the Duet Plus.
Whenever the contacts operate, the Duet Plus will
provide a warble sound from the internal speaker.
Volume and warble tone are adjustable.
To help in setting volume and tone, the TEST
button can be used to activate the Duet Plus.
If multiple units were connected to the same
contacts, then the TEST button would only activate
the particular unit being tested. When more than
one unit is connected to the same contacts then
it is necessary to ensure that all RELAY circuits
are wired in the same polarity to prevent mutual
activation.
This application is used for offices, quiet
warehouses, and common areas. The power
supply can be located in an equipment room
and provided to the Duet Plus through the same
cabling as the control contacts.
Note that the warble volume cannot be turned
completely off so that accidental adjustment is not
mistakenly considered to be a product failure.

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CO/PBX
PAGE
VOL DET
PAG
HI
LO
DET
TONE VOL TEST
PWR
SPK
OVER-CURRENT
24V
+_
J1
J2
J3
Fig. 3 - Dry Contact Office Ringer

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Loud or Outdoor Dry Contact Ringer
In this application, an 8 Ω horn speaker has
been added for significant improvement in output
volume. The Duet Plus can provide more power
than the internal speaker is capable of handling.
Only 25% of the available power is provided to
the internal speaker. The SPKR terminals provide
access to 100% of the power.
For outdoor applications, a weatherproof horn
speaker (such as Algo’s 1185) can be mounted
on an outside wall, while the Duet Plus is located
safely indoors. Besides keeping the Duet Plus dry,
this also makes tone and volume adjustment or
other maintenance easier.
The internal speaker may be left in use or
disconnected depending on option shunt J3 (SPK).
If the shunt is on, then the internal speaker is
enabled. Remove the shunt (park it on one pin
only) to disable the speaker.
The TEST button will activate the warble through
the horn speaker.

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CO/PBX
PAGE
VOL DET
PAG
HI
LO
DET
TONE VOL TEST
PWR
SPK
OVER-CURRENT
24V
+_
J1
J2
J3
8 Ohm
Horn Speaker
Telephone System
Night Bell or
Auxiliary Ring Contacts
24 Vdc
Power
Supply
24 Vdc
Power
Supply
J3
PWR
SPK
Fig. 4 - Loud or Outdoor Dry Contact Ringer

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Loud Ringer and Paging
Once a Duet Plus has been successfully installed
as a loud ringer with external speaker, the option
is available to add voice paging without any
requirement for additional equipment. Simply
connect the dry or wet page port from the
telephone system to the AUDIO INPUT terminals
of the Duet Plus. Now the Duet Plus will provide
loud ringing and paging through the same
speaker.
From the equipment room, a three-pair cable can
provide power supply, dry contacts for ringing,
and paging audio. For maximum output power,
minimize wiring resistance between the Duet Plus
and the speaker. If telephone wire is used, use
all available conductors for power to minimize
resistance.
The warble tone and volume are adjusted as for
the previous application. The paging volume may
be set independently using the PAG VOL control
on the left side of the PC Board about midway
between top and bottom.
With a typical 8 Ω horn speaker, a Duet Plus will
provide sufficient ring and paging volume for
average ambient noise warehouses up to 10,000
square feet (930 square meters).

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CO/PBX
PAGE
VOL DET
PAG
HI
LO
DET
TONE VOL TEST
PWR
SPK
OVER-CURRENT
24V
+_
J1
J2
J3
Paging Volume
Fig. 5 - Loud Ringer and Paging

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Nortel/Avaya Digital Station Set Ringer
A Duet Plus can be configured to detect audio
signal and activate warble tones when a
particular threshold is reached. The most common
application of this feature is to detect the ringing
on Nortel/Avaya TDM phones that provide ring
signal to the headset jack.
Option shunt J1 and J2 are set to DET (detect)
mode and the monitored audio connected to the
AUDIO INPUT terminals. The PAG VOL control
now adjusts detection sensitivity.
Due to the high sensitivity required for ring
detection using the headset jack, the wiring
between the station set and a Duet Plus should
not exceed more than several feet. In all cases,
adjust the station set ring volume as high as
possible, and then adjust the Duet Plus sensitivity
for threshold plus a 1/8 turn clockwise. Too much
sensitivity in electrically noisy environments can
cause false ringing.
Telephones that support this feature include:
• M3900 series TDM sets for M1 and CS1000
• M7000 series TDM sets for Norstar, BCM, and
IP Office

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CO/PBX
PAGE
VOL DET
PAG
HI
LO
DET
TONE VOL TEST
PWR
SPK
OVER-CURRENT
24V
+_
J1
J2
J3
Fig. 6 - Nortel/Avaya Digital Station Set Ringer

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Visual Alerting
A Duet Plus can provide a visual indication of
ringing by the connection of an Algo 1126 Strobe
or 1127 Visual Alerter to the SPKR terminals.
Whenever the Duet Plus is activated, the strobe or
alerter will activate. The most common application
is for visual alerting in environments that are
either exceptionally noisy or require noise-free
alerting.
When the Duet Plus warble had been activated the
speaker output can be used to activate the strobe
or visual alerter.