ASL INTERCOM PS 278 User Manual page 6

5.0 FRONT PANEL CONTROLS
10 VOLUME control knobs
These knobs adjusts the listen level for the headset.
Each channel can be adjusted separately.
11 SIDETONE trimmers
These trimmers adjust the level of your own voice as
you hear it in your headset.
Adjustment procedure :
- set the trimmer in start position: fully clockwise.
- switch off the microphone of all connected
(speaker!) stations.
- switch on the microphone of the required channel.
- turn up the volume of the required channel.
- speak into the headset microphone.
- adjust the listen level by turning the sidetone
trimmer.
The operating area is between fully clockwise and
minimum level. Adjusting the sidetone does not affect
the level of your voice as it is heard by other stations.
12 TALK buttons
These buttons allow you to talk to each channel
separately or simultaneously.
The large green LED indicates if the talk function is
activated.
Latched switching:
When a TALK button is momentarily pressed, the
microphone will be switched on for the chosen channel
and is electronically latched. When pressed again, the
microphone will be switched off.
Momentary switching:
When a TALK button is pressed and held, the
microphone will be switched on, and when released,
will be switched off.
User Manual PS 278 / Issue 2 © 1996 ASL Intercom, Utrecht, Holland.
13 CALL A & B buttons
These push buttons activate the CALL system.
A momentary push will send a CALL signal to all
stations connected to that intercom channel and the
CALL LEDS will start flashing.
Press and hold the buttons for 2 seconds will activate
the call buzzer, if not muted.
After the CALL button is released the LEDS will
continue to flash for a further 2 seconds.
14 HEADSET connector
A XLR-4 type connector for the connection of the local
headset. This must have a can impedance of 200
ohms (or greater), or each 400 ohms minimum when in
parallel. The mic may be of the dynamic or electret
type.
Pin assignments:
1. shield mic. (GND)
2. mic. +
3. phones +
4. phones -
The wiring is such that both headset cans are
connected in parallel and receive the same signal. The
two headphone amplifiers run in a bridged mode.
As an option, a XLR-6 type connector can be fitted to
give a binaural headset configuration where a different
signal will appear on each can. In this mode the
internal headphone amplifiers are not bridged.
See section 7.1 Internal Jumpers and Controls.
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