Cabling - ASL INTERCOM PS 19 A User Manual

9.0

CABLING

The intercom lines (the 'party lines') in an ASL analog intercom system are of the shielded two-conductor
microphone cable type. The intercom line connectors are of the XLR-3 type. Audio and Call signals are on
pin 3, DC power is on pin 2 and pin 1 is connected to the shield of the cable which functions as the
common return for audio and power.
The audio signal is transferred in an unbalanced way (see 'Party Line, Technical Concept').
To avoid earth loops (hum), the possible effect of electromagnetic fields and to minimize power loss, certain
rules have to be obeyed when installing the cabling of an intercom system :
Use high quality cable
Use high quality microphone cable (shielded two
conductor cable, minimum 2x 0.30 mm2). In case
multi-pair microphone cable is used, there should
be an overall shield and each pair should consist
of two conductors (minimum 2x 0.15 mm2) with
separate shield
Use flexible cable
Use flexible single and multi-pair microphone
cable instead of cable with solid cores, especially
when the cable is subjected to bending during
operation or installation.
Cable screens to XLR pin 1
The screen of each separate microphone cable
and/or the screen of each single pair in a multi-
pair cable, should be connected to pin 1 of each
XLR-3 connector. Do not connect these screens
to the metal housing of ASL units or XLR-3 wall
boxes.
See section 'Earthing Concept'.
Connect metal cable trunks, wall boxes and
overall multi-pair cable screens to clean earth
Metal cable trunks, metal wall boxes and overall
multi-pair cable screens should be interconnected
and, at the 'central earth point' in the intercom
network only, be connected to a clean earth or a
safety earth.
See section 'Earthing Concept'.
Keep metal connection boxes and cable
trunks or pipes isolated from other metal parts
Metal trunks or pipes for intercom cables and
metal connection boxes should be mounted in
such a way that they are isolated from any other
metal housing or construction part.
In case of more complex installations, don't hesitate to contact us. Please send us a block diagram of the
planned network with a list of all user stations and their positions, and we are happy to advise you on
cabling lay out.
Keep cables parallel as much as possible
When two (multi channel) units in a network are
connected by more than one cable, make sure
that these cables are parallel to each other over
the whole distance between those units. When
using multi-pair cable, parallelism is ensured in
the best possible way.
Avoid closed loops
Always avoid that intercom cables are making a
closed loop. So-called 'ring intercom' should not
physically be cabled as a ring..
Keep cables away from electromagnetic
sources
Keep intercom cables away from high energy
cables, e.g. 115/230/400V mains power or
dimmer controlled feeds for spotlights. Intercom
cables should cross high energy cables at an
angle of 90º only. Intercom cables should never
be in the same trunks as energy cables.
Place power supply in a central position
In case of a system powered by a separate power
supply: In order to diminish power losses, place
the power supply as close as possible to where
most power consumption occurs, in other words
most user stations are placed.
ASL powered units to a 'clean' mains outlet
Master stations or power supplies should be
connected to a mains outlet with a clean earth.
Other audio equipment may be connected to this
mains outlet, but avoid using an outlet which also
powers dimmer controlled lighting systems.