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

As an intercom station 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.

In Parallel with an Intercom Station
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.

Remote control of Amplifier
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.
→ NOTE: Another way to get a “vol_override control signal” is to take it from a switch connected to the announcement microphone.
→ 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
  

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.

Front Potentiometers

Volume Control

The potentiometers are accesible through holes in the front plate for adjusting:

• Ordinary volume output
• Volume for the volume override function

Equalizer Control

The potentiometers are accessible through holes in the front plate for adjusting:

• Bass (Eq. low)
• Treble (Eq. high)

Reset and Set Keys

The reset key restarts the internal processor. An automatic line-test is performed after each reset. The reset signal can be triggered via an external input which makes it possible to activate the reset function from a central control room. In conjunction with the set key, the reset key is also used during commissioning of the amplifier.

The set key is used for programming and for setting new line impedance references.

The keys are behind the front plate and can be reached with a thin pen.

LED Indications for Error Reporting

The LEDs are hidden behind the front plate, but the light can be seen through the potentiometer slits.

2 LEDs for status: Power-on, Overload (clipping).

3 LEDs for line-errors: Line-short, Load-error Ground-fault.

2 LEDs for amplifier errors: Amp-error, Over-temp.

See error reporting details on page 139.

The Load-error LED has two functions, Load-error (light on) and Line-open flashing).

During programming the LEDs take on a different meaning - see page 138.

Line Monitoring and Error Reporting

The amplifier has a built-in monitoring function for the output line. The built-in monitoring checks the line to the loudspeakers for load changes, open or shorted line and ground faults.

If the amplifier is connected to an AlphaCom exchange as a station, the abcd-wires are included in the system line monitoring feature. If the amplifier is connected in parallel with a station, it has no monitoring, as the ab- and cd-wires are not terminated.

It is possible to use the amp_error relay and/or line_error output as an RCI input to the AlphaCom exchange. In this way, for example, a text message can be sent to a station when there is an error on the amplifier.

The AUX input wires have no monitoring.

Reference impedance for line monitoring, time between line tests and error detection limits can be programmed at the amplifier. The set and reset keys in the front panel are used for the programming.

Monitoring modes of loudspeaker lines

The amplifier has 2 line monitoring modes with different error limits. It is also possible to adjust the time between the line tests. The default settings are 5 W mode and 20 seconds.

• Standard mode:

the amplifier detects loudspeaker load errors of 5 W or more. The time interval is 20 seconds.

• In Rough mode:

the amplifier detects loudspeaker load errors of 15 W or more. The time interval is 20 seconds.

When used as a standalone amplifier, the line monitoring can be is set to occur only once every 24 hours. But it will still monitor the line and display errors by means of LED indicators.

Amplifier errors

The amplifier checks internal references and the temperature of the output stage. If the amplifier detects an internal error it will report amp_error with LED and relay driver output, but still try to operate.

If the amplifier detects overheating, it will report amp_error and turn on the over_temperature LED and shut down temporarily to cool off. It also operates an output for changeover to a possible standby amplifier.

Shortly before the amplifier goes to shutdown it will reduce the output level with 50% and start flashing the over_temperature indicator.

Additional Information

→ Reducing the output level reduces the generated heat and may in many cases be enough to stop a total shutdown. During this period the output power will be max. 30 W. → An overheating shutdown is not a fatal error and may happen if the amplifier is driven very hard. It is a safety mechanism where the amplifier shuts down the output stage to avoid thermal destruction. The amplifier will automatically resume operation when it has cooled down.

Line errors

The amplifier can detect a shorted line, open line, load error, or ground fault. The faults have different detection ranges; see below.

Loudspeaker lines are tested only when the amplifier is in standby.

The total line capacitance must not exceed 27nF. (About 300 m of 90 nF/km cable.)

For ground fault detection, "Battery minus" must be connected to "mains earth".

Error Reports

The amplifier will report both amplifier and line errors in three ways.

• A LED on the front panel will light or flash to indicate type of error (see fig.

Figure 13-8).

• The amplifier shorts the cd-pair for 60 sec. to give a “general fault” to the

AlphaCom exchange.

• One or both relay drivers are deactivated to give a “general fault” message - see

description below. For more details on error reports, see page 139.

Additional Information

The amplifier always continues to work, regardless of the errors indicated. The exception is a

controlled shutdown due to overheating.