ASL INTERCOM PS 6379 MK2 User Manual page 29

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 must be obeyed when installing the cabling of an intercom sys-
tem:
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, es-
pecially 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 inter-
connected 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.
Keep cables parallel as much as possible
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