ASL INTERCOM BS 181, User Manual

Page: 6 / 11

User Manual BS 181 / Issue 1 © 1998 ASL Intercom, Utrecht, Holland.
6
7.0 CABLING
For the BASIC 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
¼ ¼
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:
Use high quality (multipair) cable. Keep cables parallel as much as possible.
For interconnecting user stations, power supplies and When two (two channel) units in a network are
accessories in an ASL Intercom network, use high connected by more than one cable, make sure that
quality shielded two-conductor (minimum 2x 0.30 mm2) these cables are parallel to each other over the whole
microphone cable only. distance between those units. When using multipair
In case of a two channel intercom network, use high cable, parallelism is ensured in the best possible way.
quality microphone 'multipair' cable only, each pair
consisting of two conductors (minimum 2x 0.15 mm2)
with separate shield. Multipair cable should also have
Always avoid that cables are making a loop. So-called
an overall shield. 'ring intercom' should not physically be cabled as a
Use flexible cables.
Use flexible single and multipair microphone cable
power supply position) as the centre of the star.
instead of cable with solid cores, especially when the
cable is subjected to bending during operation or
installation.
Keep intercom cables away from high energy cables,
Separate cable screen to XLR pin 1.
The screen of each separate microphone cable and/or
Intercom cables should cross high energy cables in at
the screen of each single pair in a multipair cable, angle of 90
(
only.
should be connected to pin 1 of each XLR-3 connector. Intercom cables should never be in the same trunking
Do not connect this cable screen to the metal housing as energy cables.
of the connector or to metal wall boxes (outlets).
See page 10 for Earthing Concept.
Cable trunks, connection boxes and overall
multipair cable screen to clean earth.
Metal cable trunks, metal connection boxes and overall
user stations are placed.
multipair cable screen should be interconnected and,
at one point (the 'central earthing point') in the intercom
network only, be connected to a clean earth or a safety
earth.
The ASL power supply may be connected to the mains
See page 10 for Earthing Concept. power outlet to which other audio equipment is
Keep metal connection boxes and cable housings
isolated from other metal parts.
Metal housings for intercom cables and connectors
In case of more complex installations, don't hesitate to
should be mounted in such a way that they are isolated contact us. Please send us a block diagram of the planned
from other metal cable and connector housings and network with a list of all user stations and their positions,
from any other metal construction parts. and we are happy to advise you on cabling lay out.
¼ ¼
See Party Line, Technical Concept
Avoid closed loops.
ring. All cable routes should have a 'star' configuration,
with the central earthing point (usually close to the
Keep cables away from electromagnetic sources.
e.g. 110/220/380V mains power or dimmer controlled
feeds for spotlights.
Place power supply in a central position.
In order to avoid unacceptable power losses, place the
power supply as close as possible to where most
power consumption occurs or, in other words, most
Connect ASL power supply to a 'clean' mains
outlet.
connected. Avoid using mains outlets which also power
dimmer controlled lighting systems.