View source for IG60 - InterGuard 60W Amplifier

The InterGuard 60 W Amplifier  is available in two versions, for 100 V and 50 V
loudspeaker lines.

== Areas of Use - Features ==
The amplifier is intended for use with AlphaCom exchanges for distributing voice
evacuation messages, information calls, background music or any other audio
signals.

Because the AlphaCom is a wide-bandwidth audio switch, it is well suited for
routing high-quality audio to output subscriber lines. The IG60 input is then
connected to the a-b subscriber pair and the amplified audio is distributed out on
100 V rms. or 50V rms. loudspeaker lines.

An additional separate AUX input is available on the IG60 for direct connection of
radio tuners, CD players, etc.

A Volume Override facility is provided for messages that need extra attention.

The Loudspeaker Line Monitoring detects changes in loudspeaker load and reports
the errors by means of LED indicators on the amplifier. It also shorts cd-wires, and
sends a general fault message as well as a signal to the internal line error relay
driver. The amplifier also monitors its own functions and performs a controlled
shutdown at over-temperature.

It reports any amplifier errors by means of LED indicators, sends a general fault
message to the AlphaCom exchange and operates a relay driver that can be used
for automatic changeover to a standby amplifier.

== Audio Connections ==
=== Connection Options ===
The amplifier is connected to an AlphaCom exchange through the abcd-wire input
and to another audio source through the AUX input. The abcd and AUX inputs can
both be connected, but audio on the abcd-wires then has priority over the AUX
input.

The connection options are:
* To the AlphaCom exchange as a station:
** A single amplifier on one subscriber output.
** Several amplifiers in parallel on one subscriber output.
** As standby amplifier to another IG60.
* In parallel with a station in an AlphaCom exchange.
* As a stand-alone amplifier to an AUX source.
* To both AlphaCom and AUX at the same time.

=== Amplifier Connected to AlphaCom Exchange ===
<u> As an intercom station </u>
The amplifier is connected to the abcd-wires in an AlphaCom exchange in order to
amplify the audio on the subscriber lines. The exchange sees the amplifier as a
subscriber station.

The ab-pair is the loudspeaker pair, while the cd-pair is the microphone pair. The
cd-pair is also used for current detection of the station.

The IG 60 amplifies the audio on the ab-pair. One􀀀ab-pair can be connected to 21
amplifiers in parallel, but only one amplifier can terminate the ab-loop. The
amplifier can be turned on by the presence of audio on the ab-pair, or by an active
AMP_ON control signal.

The amplifier can further be connected to the cd-pair. This serves two purposes:
* If the cd-pair is terminated, a polarity change on the cd-pair will also turn the
amplifier on.
* The amplifier can send an error message back to the exchange by shorting the
cd-pair.

One cd-pair can have up to 21 amplifiers connected in parallel, but only one
amplifier can terminate the cd-loop (Set switch S6-2 ON).

==== Additional Information ====
→ You can connect 21 amplifiers in parallel to an AlphaCom exchange. Note the following
limitations:
:: → The RCO signal from the AlphaCom can only drive one amplifier input. The RCO signal must therefore be increased with an external driver if you want to use it on more than one amplifier. For this purpose the MRBD board can be used.
:: → It is possible to set the amplifier so that it is forced on when polarity is switched on the cdpair. If parallel amplifiers are used, only one of the amplifiers can be turned on this way.

<u>In Parallel with an Intercom Station</u><br>
The amplifier can be connected to the abcd-wires in parallel with an intercom
station, amplifying the audio to that station. The station can be used as usual, for
example to answer group calls and make outgoing calls.

<u>Remote control of Amplifier</u><br>
The audio on the ab input can also be switched on by the AMP_ON remote control
signal.

=== Amplifier used to distribute other audio (Standalone) ===
The amplifier can also be connected to another audio source like a CD player,
radio or other type of audio through the AUX input. The amplifier is then switched
on by the presence of audio on the AUX input. The AUX input sensitivity can be
either 100 mV or 1 V, which you can select by DIP-switch setting. There is no
control signal to keep the amplifier on permanently. During pauses and very low
audio input, the amplifier will go into standby mode after 5 seconds.

The IG60 can also be used as a standalone amplifier when connected to the AUX
input. Set the line monitoring to occur only once every 24 hours.

==== Additional Information ====
→ The AUX input is 600 ohm. Several amplifiers in parallel may overload the source.

=== Audio Priorities ===
If all audio input and control options are used, the audio priorities are:
* Level 3 (highest) Activated AMP_ON control or polarity change on c-d  pair. Uses audio from ab-pair input.
* Level 2           Audio on ab-pair (squelch). Uses audio from ab-pair input.
* Level 1           Audio on AUX pair (squelch) (not if level 2 or 3 occurs). Uses audio from AUX input.

=== Audio Output Adjustments ===
The amplifier has two controls labeled “volume” and “vol. override”, as well as
bass (EQ low) and treble (EQ high) controls. All four are accessible at the front.

The amplifier also has an overload LED to help to adjust the amplifier gain and
input signal strength. If the overload LED flashes, the output signal is being
clipped.

Normally, both a-b wire and AUX signals are amplified as set by the VOLUME
potentiometer. To obtain different output levels, the output signals from the
different audio sources must be adjusted.

When the external “vol_overr.” control signal is activated, the volume is set by the
VOL. OVERRIDE potentiometer. The volume setting applies to both a-b wire and
AUX signals.

Below is an application example of how the volume override function can be used:

: Very low audio (background music, etc.) from one source is interrupted with loud audio (voice messages) from another source. Both music and messages come from the AlphaCom’s ab-pair. The music can then use the (normal) VOLUME potentiometer, set at low gain, while the messages are accompanied by an external “vol_overr control signal” that switches to the VOL. OVERRIDE potentiometer with high gain.

==== Additional Information ====
→ NOTE: The “vol_override control signal” can be activated by a RCO (Remote Control Output) signal from the AlphaCom. The RCO signal must be programmed to become active whenever a call or group call is set up to that subscriber position, but not if music is set up.<br>
→ NOTE: Another way to get a “vol_override control signal” is to take it from a switch connected to the announcement microphone.<br>
→ NOTE: The RCO signal from the AlphaCom can only drive one amplifier input. If several amplifiers are used in parallel, the signal must be increased with an external driver.

== Front Panel Control and Indicators ==
At the front you will find the following controls and indicators:
* Volume controls
* Equalizer controls
* Set keys
* LED indicators for error reporting<br>
Through the holes for the potentiometers on the front plate, you can see 7
LEDs which are used for status and error reporting. The LEDs are also used
for indicating values during commissioning.