User manual
User Manual PS 630 / Issue 1 © 1994 ASL Intercom, Utrecht, Holland.
8
microphone.
20 GOOSENECK MIC GAIN
This trimmer controls the gain of the gooseneck
microphone.
7.0 CABLING
For the PRO Series Intercom system the
interconnecting cables are of the shielded two-
conductor microphone cable type and the intercom
line connectors are of the XLR-3 type. Audio and Call
signals are on XLR pin 3, DC power is on XLR pin 2.
XLR pin 1 is connected to the shield of the cable
which functions as the common return for audio and
power.
Since the audio signal is transferred in an
unbalanced way, certain rules have to be obeyed
when installing the cables of an intercom network.
This is to avoid earth loops and to minimize power
loss and the possible effect of electromagnetic
fields.
These rules are:
o Use high quality (multipair) cable. o Keep metal connection boxes and cable trunks
For interconnecting user stations, power supplies isolated from other metal parts.
and accessories in an ASL Intercom network, use Metal housings for intercom cables and connectors
high quality shielded two-conductor (minimum 2x should be mounted in such a way that they are
0.30 mm2) microphone cable only. isolated from other metal cable and connector
In case of a multi channel intercom network, use housings and from any other metal construction
high quality microphone 'multipair' cable only, each parts.
pair consisting of two conductors (minimum 2x
0.15 mm2) with separate shield. Multipair cable o See Party Line, Technical Concept
should also have an overall shield.
o Use flexible cables. connected by more than one cable, make sure that
Use flexible single and multipair microphone cable these cables are parallel to each other over the
instead of cable with solid cores, especially when whole distance between those units. When using
the cable is subjected to bending during operation multipair cable, parallelism is ensured in the best
or installation. possible way.
o Separate cable screen to XLR pin 1. o Avoid closed loops.
The screen of each separate microphone cable Always avoid that cables are making a loop. So-
and/or the screen of each single pair in a multipair called 'ring intercom' should not physically be
cable, should be connected to pin 1 of each XLR-3 cabled as a ring. All cable routes should have a
connector. Do not connect this cable screen to the 'star' configuration, with the central earthing point
metal housing of the connector or to metal wall (usually close to the power supply position) as the
boxes (outlets). centre of the star.
See page 10 for Earthing Concept.
o Cable trunks, connection boxes and overall Keep intercom cables away from high energy
multipair cable screen to clean earth. cables, e.g. 110/220/380V mains power or dimmer
Metal cable trunks, metal connection boxes and controlled feeds for spotlights.
overall multipair cable screen should be inter- Intercom cables should cross with energy cables at
connected and, at one point (the 'central earthing an angle of 90 degrees only.
point') in the intercom network only, be connected Intercom cables should never be in the same
to a clean earth or a safety earth. trunking as energy cables.
See page 10 for Earthing Concept.
o Keep cables parallel as much as possible.
When two (multi channel) units in a network are
o Keep cables away from electromagnetic sources.