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PAGE 6
User manual PS 155 / Issue 2011 © ASL Intercom BV
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8.0
THE CABLE TO THE WIRELESS UNIT
This section describes the connection between
the PS 155 and the wireless unit and the
connection between the PS 155 and an external
PTT switch.
At the wireless unit the connection cable is
plugged into the connector which is normally
used to connect a speaker/microphone device.
At the PS 155 the cable is plugged into Sub-D9
connector at the rear panel.
Pin assignment of the Sub-D9 connector:
Pin 1: Audio input -
Pin 2: Audio input +
Pin 3: PTT button switch
Pin 4: Transmit switch (Common)
Pin 5: Transmit switch (Normally Open)
Pin 6: Transmit switch (Normally Closed)
Pin 7: Ground/shield
Pin 8: Audio
Pin 9: Audio output -
Pin 1 and 2 :
The Audio Input is transformer balanced,
decoupled with capacitors to obtain a high DC
resistance. If the wireless unit uses asymmetric
signal transport then the audio input - (pin 1) is to
be connected to the ground of the wireless unit
and (if necessary) to pin 7 of the Sub-D 9
connector.
Pin 8 and 9 :
The Audio Output is transformer balanced,
decoupled with capacitors to obtain a high DC
resistance. If the wireless unit uses asymmetric
signal transport then the output - (pin 9) is to be
connected to the ground of the wireless unit and
(if necessary) to pin 7 of the Sub-D9 connector.
The gain of the Audio Output can be adjusted by
internal trimmer R4, see section 11.0.
Pin 3 and 7 :
An external PTT (Push To Talk) button may be
connected to these pins of the Sub-D9 connector.
By pushing the PTT button the wireless unit is
triggered to go from receive mode to transmit
mode. De PTT button only works if the TX
CONTROL select switch (#9) is set in position
³377´
Pins 4, 5 and 6 :
The Transmit Switch contacts are located
between these pins of the sub-D9 connector.
Normally Open:
Most wireless units need a contact to be
closed to go from receive mode to
transmit mode. Use pin 4 and 5. Some
wireless units need to see a special DC
resistance. Ask the manufacturer of the
wireless intercom system to advise you on
what value of the resistor to use. Usually
the resistor is to be mounted in the
Common wire of the Transmit Switch
contacts. See also drawings below.
Normally Closed:
Some wireless units need a contact to be
opened to go from receive to transmit
mode. Use pin 4 and 6.
Important notices:
Use high quality cables and connectors
Make sure that all interconnecting cables
are properly shielded. This to avoid RF
interference of the wireless intercom system
and the wired ASL intercom system
If possible, use a balanced audio
connection to and from the wireless unit.
Using a cable assembly from the wireless
intercom manufacturer is to be preferred.
Make sure that the connections made to the
wireless unit are according to the
specifications of its manufacturer
Always use the by ASL supplied Sub-D9
connector cable part; this connector is
shielded
To avoid RF interference, place the wireless
unit not to close to the PS 155 and the
intercom cables. But the connection cable
should not be too long.
