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Installation
Description of Phantom-Powered Connection
An example of a phantom-powered system. In this system a PS-2001L power supply is set to isolate mode. In
FIGURE 4.
this mode each channel is a separate party line and current per channel is limited to 1 amp. Note, both single and two-
channel intercom stations may be connected by using "Y" cables (or JB2 Junction boxes). Pre-fabricated cables may be
used, or cables may be constructed using the diagrams in Figure 10 on page 14.
In this method, operating power and intercom audio for the entire system are carried over the same wires. The advantage of
this method is simplicity of connection. The system power supply (PS-2001L, SPS-2001A, etc.) automatically provides what
is known as a terminating impedance for the intercom system. Without this terminating impedance, the sound quality will be
distorted, and the levels will shift every time additional stations are connected. The disadvantage of the phantom power
method is that some operating power is lost over very long intercom cables, and performance at distant 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 4 illustrates a phantom
power intercom system.
NOTE: 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
automatically disconnects from the systems's phantom-power supply.
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