PAGE 5
User Manual PS 155 / October 2013 © ASL Intercom BV
.
5.0 RECEIVE AND TRANSMIT MODE
If the internal Transmit Switch of the PS 155 is
triggered, the wireless unit connected to the PS
155 (see section 8.0) goes from ‘receive mode’
to ‘transmit mode’. The Rx/Tx LED (#11) goes
from being lit green to being lit red. The Transmit
Switch can be triggered in three different ways,
to be selected by a 3-position switch in the TX
CONTROL section of the PS 155 front panel.
These switch positions are:
‘CALL’
Transmit mode is enabled by pushing any CALL
button at the wired intercom stations. Detect of
this Call signal triggers the Transmit Switch.
When this option is selected, the buzzers of all
user stations connected to the party line are
automatically disabled. The Call Detect level can
be adjusted by trimmer R29, see section 9.0.
‘VOX’
Transmit mode is enabled by detecting audio on
the intercom party line. As soon as this audio
signal exceeds an adjustable threshold, the
Transmit Switch is triggered. The VOX has a
special frequency contouring circuit which is
optimized for the human voice.
The attack (threshold) level and the release time
can be adjusted at the front panel.
The attack time can be adjusted by trimmer R9,
see section 9.0.
‘PTT’ (Push To Talk)
Transmit mode is enabled by pushing an external
button, to be connected to the PS 155.
This push button should be momentary only.
See also section 6.0
6.0 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 output +
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
trimmer R4, see section 9.0.
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 switch (#9) is set in position
“PTT:”
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.
(10 paginas)
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