Intercom Channel Connections
The method of connection depends on the type of box. The “S” box and “P” box ver-
sions connect to the intercom system using prefabricated cables in a phan-
tom-powered configuration, as described below and illustrated in Figure
4
. The “U”
box version is designed for permanent installation, and it can be either phantom pow-
ered or locally powered. Examples are shown in Figures
6
and
7
.
Description of Phantom Powered Connection
In this method, operating power and intercom audio for the entire intercom system
are carried over the same wires. The advantage of this method is simplicity of con-
nection. Also, the system power supply (PS2000L, SPS2000A etc.) automatically
provides what is known as a terminating impedance for the intercom system. Without
this terminating impedance, the sound quality will be very distorted, and the levels
will shift every time additional stations are connected. The disadvantage of the phan-
tom power method is that some operating power is lost over very long intercom ca-
bles, and performance at distant intercom stations may be reduced. Generally, if
intercom stations are within a few hundred feet from the system power supply, phan-
tom power will be sufficient. Also note that increasing the number of stations will re-
duce the overall operating distance. Phantom power is generally the only method that
will be used to connect the “S” and “P” box versions, since these versions are usually
connected with relatively short cables of less than 200 ft. Figure
4
, page
13
, illus-
trates a phantom powered intercom system with "S" and "P" type stations. Figure
6
,
page
15
, illustrates phantom power for "U" boxes.
Note that the distance over which power can be delivered is less than the distance
over which audio can be delivered. Audio can be delivered for several miles to lo-
cally powered stations as described below.
Description of Locally Powered Connection
☞
Only the "U" box has provisions for local power. The 3-pin connectors on the
"S" box and "P" box do not permit this type of connection.
1 1
