Formula Sound AT-1 User manual
AT-1 VOLUME CONTROLLER
USER MANUAL
TheAT-1 is available in two case styles as shown above.
One is a 19” rack mount case the other is a free standing or
wall mounting case. The connections to the units and their
operation is identical.
AT-1 VOLUME CONTROLLER
Introduction
TheAT-1 has been designed to be used in conjunction with the SENTRY MK2 environmental noise control unit. It is a
digitally controlled stereo unit and its purpose is to control the volume level of an audio system connected to it, without
cutting off the system completely. It will control the connected system to the maximum level allowed as defined by the
Sentry Mk2, thus removing the worry of having to continually watch levels. It does this without affecting the dynamic
range of the music being played, and because the control chain is microphone driven the amount of absorption which
takes place when a venue is full of people is automatically catered for.
More than one unit may be connected to the SENTRY MK2 to control more than one audio system. This is particularly
useful as it means that the house system and a visiting system, band, etc. can be controlled to the same maximum
level. The Sentry will automatically control theAT-1 that is in use.
It is in the interests of a visiting band or DJ to connect to theAT-1 where a Sentry is installed so that they do not suffer
the embarrassment of being cut off if they play too loud.
In the past control units monitored the signal level passing through a system to control the maximum level available.
This approach works fine but the system has to be calibrated to determine the relationship between the signal level and
the actual sound pressure level being produced. This makes it impractical to control visiting systems by this method.
This has now changed with the introduction of theAT-1. Because the control information is derived from a microphone
system (i.e. The Sentry) calibration is no longer required; therefore any system may be connected and controlled
bearing in mind a few common sense points. If the visiting system is not connected to theAT-1 the Sentry switching the
available mains power in the usual manner will control it. We feel that this will encourage visiting systems to connect to
theAT-1.
CONNECTIONS TO THE SENTRYMK2
THESE CONNECTIONS MUST BE AS LISTED BELOW
A 4 CORE CABLE IS REQUIRED - ALARM CABLE OR SIMILAR SHOULD BE USED. IF IT IS
SCREENED (WHICH IS RECOMMENDED FOR LONG RUNS) CONNECT THE SCREEN TO PIN
1 OR MIC SCREEN
AT-1 CONNECTOR SENTRYTERMINAL
PIN 1 REMOTE MIC SCREEN
PIN 2 SLAVE OUT +
PIN 3 WARNING LED
PIN 4 12 VOLT CONTACTOR +
SWITCHON
When first switched on theAT-1 will be at full attenuation. When the Sentry is reset the unit will fade to no attenuation.
This will take several seconds and is quite normal.
The Sentry timer should be set at about 20 seconds (mid point on timer pre-set), this is the factory setting. If the Sentry
is tripped for any reason (security loop broken, Mic tamper, etc) the AT-1 will go to full attenuation.
CALIBRATION.
N.B.DO NOT PRESS THE CALIBRATION BUTTON UNTILTHE DISPLAY IS SHOWINGACONSTANT 0dB
Calibration is recommended when using the unit for the first time with a particular Sentry To do this proceed as follows:-
with no inputs connected to theAT -1 generate a sustained noise that lights the Sentry display to the amber LED 0dB
point (a note on a keyboard or a tone generator is useful for this). Then press the CALbutton on the rear of theAT-1
using a small screwdriver or similar. This procedure will give the most accurate control and allows for any component
tolerance between Sentrys. If not carried out the unit will still work.
Users cannot cheat as the unit will accept only a small range of adjustment to compensate for component tolerance.
OPERATION
Connect theAT-1 between the mixer and power amps using the jacks or XLRs provided. The system volume will be
controlled if necessary as determined by the sound pressure level (SPL) which the Sentry Mk2 Is set at.
The fade times will vary depending on the amount that the SPL threshold has been exceeded.
220-240V
A.C.
FUSE
250mA
A/S
SEE
MANUAL
FOR 115V
OPERATION
2143
CAL
FORMULA SOUND AT1 AUTOMATIC VOLUME ATTENUATOR. MADE IN ENGLAND
XLRS PIN 1 - SCREEN. PIN 2 - PHASE. PIN 3 - NON PHASE. JACKS 3 POLE BAL, 2 POLE UNBAL.
S/No
LEFT INPUTRIGHT INPUTRIGHT OUTPUT LEFT OUTPUT
CONTROL CONNECTIONS
FROM SENTRY.
SEE MANUAL
XLRS OR JACKS MAY BE USED
FOR INPUTS AND OUTPUTS
CONNECT TO AMPLIFIER INPUTS
EITHER JACKS
OR XLR CONNECTORS
MAY BE USED
SEE PREVIOUS PAGE FOR DETAILS
4 CORE CABLE TO SENTRY MK2
LOUD SPEAKER
SYSTEM
POWER AMPLIFIERS
MIXING CONSOLE OR PRE-AMP UNIT
EITHER JACKS
OR XLR CONNECTORS
MAY BE USED
ABOVE IS SHOWN A TYPICAL CONNECTION TO THE AT1
DO NOT!!
CONNECT AMPLIFIER OUTPUTS OR LOUDSPEAKERS
DIRECTLY TO THE AT-1 AS PERMANENT DAMAGE MAY
RESULT
NOT ALL AUDIO SYSTEMS ARE SUITABLE FOR CONNECTION TO THE AT-1
THE UNIT WILL ONLY WORK WITH AUDIO SIGNALS AT CERTAIN LEVELS.
IF YOU ARE NOT SURE IF YOUR SYSTEM IS COMPATIBLE CONSULT AN
AUDIO SPECIALIST OR THE MANUFACTURERS OF THIS UNIT.
Specification
Case Styles Two versions are available: - a 19” 1RU unit, and a free standing or
wall mounted unit which may be more convenient for connecting to
visiting systems.
Dimensions 19” 1RU version.
19” 483mm wide 1.75” 45mm height 4.9” 125mm depth exc
connectors.
Free standing version
15.55” 395mm wide 1.87” 48mm height 4.9” 125mm depth exc
connectors.
Input connectors 2 X ¼” 3 pole jacks which will also accept 2 pole jacks.
2 X 3 pin XLRs.
Output connectors 2 X ¼” 3 pole jacks which will also accept 2 pole jacks.
2 X 3 pin XLRs.
Using 2 pole jacks will automatically convert the inputs or outputs to
unbalanced operation.
To use XLRs unbalanced connect pins 1 and 3 to screen.
Control connector 1 X 4 pin connector. The mating half is supplied and features screw
terminals. (4 core cable connects to Sentry Mk2)
Maximum input level +20dBu.
Maximum output level +20dBu into a 600 ohm load at <.01% distortion.
Input impedance 20K ohms balanced, 10K ohms unbalanced.
Noise EIN -90 dBu.
Attenuator range Unity Gain to -90dB.
Led Indicators. -3dB, -6dB, -9dB, -12dB, -15dB, -18dB, attenuation. Input Clip.
Mains power IEC connector fused @ 250mA. 220 or 110VAC may be specified.
Finish Front and rear panels black anodised aluminium
Covers black plastic coated steel.
noiselimiters.co.uk
Lime Technologies, UK
