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intercom stations may be reduced. Generally, if intercom stations are within a few hundred feet from the system power supply,
phantom power will be sufficient. Also note that increasing the number of stations will reduce the overall operating distance.
Phantom power is generally the only method that will be used to connect the “S” box, “P” box, and RM versions. Figure 5
illustrates a phantom powered intercom system.
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 locally powered stations as described below.
Description of Locally Powered Connection
Using this method, an intercom station is connected to the intercom line just like any phantom-powered intercom station,
except that a local power supply is also connected. This local power supply is located with the intercom station and provides
power for that station only. Since power loss on the intercom lines is no longer an issue, the operating range is now limited
only to the audio transmission range, which is several miles. Another advantage to this method is that more stations can be
connected to the intercom channels. When local power is supplied to an intercom station, the station detects this and automati-
cally disconnects from the system’s phantom power supply.
Figure 6 illustrates an intercom system with both phantom powered and locally powered “U” boxes. As long as a system
power supply (PS-2001L, SPS-2001, etc.) is located somewhere in the intercom system, the proper terminating impedance
will still be suppled for all stations. However, if all stations are locally powered, and there is not system power supply, a
special line termination must be installed.
Figure 6 - A two-channel Audiocom intercom system using a PS2001L power supply. the PS2001L is set to isolate mode. In isolate mode,
each intercom channel is a separate party line, and total current for each channel is limited to 1 amp. Note that both SS1002 and SS2002
stations may be connected depending on each location’s need to communicate with one or two channels. SS1002 stations may be
connected to either channel one or two. Also note that locally powered stations may be connected. This is recommended when stations are
installed at remote locations. Since the PS2001L provides termination for the intercom channels, no user-installed termination is required.