P S - 7 0 4 F O U R - C H A N N E L P O W E R S U P P L Y
2 - 3
WIRING
When considering how to wire an intercom system, several factors must be taken
into account. These include the number of stations, the length of the cable runs
and whether single or multiple channels are preferred. If multi-channel stations
are connected with multi-pair cables, then crosstalk becomes an important issue.
(Crosstalk is not a factor with single-channel systems or multi-channel systems
where each channel is run on its own individual cable to single-channel remote
stations.) While the physical considerations include ease of installation, type of
cabling, station location, etc., the electrical considerations are concerned
primarily with the capacitance between conductors on the intercom line and the
DC resistance in the ground return of the intercom line.
Caution: Pin #1 and the shell of the
XLR
plug on the interconnect cables should
NOT be connected together.
Excessive resistance in the conductors of the cable results in a loss of sidetone null
at remote stations and some overall loss of level. Excessive resistance in the
ground connector or shield greatly increases crosstalk between channels. This can
greatly affect the performance of multi-channel systems.
SINGLE-CHANNEL SYSTEM
In a single-channel system, there are two general methods of wiring remote
stations to the power supply. Any one method may be used exclusively in a small
system and both may be used in various combinations for a larger system.
1.
Daisy Chain:
Remote stations are wired from one station to the next and so
on along each line connected to the power supply. This requires the least
amount of cable, but may be impractical due to the system layout. Also, if a
break occurs in the line, all stations downline of the break will be
disconnected from the party line.
Figure 2-1: Daisy Chain
P S - 7 0 4
