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power would be supplied on channel 2 of a connector, or
not at all. In this case, you have 3 alternatives:
1) Assign different channels to the RM-325 so that it
will receive power on channel 1
2) Reconfigure the RM-325 to receive power on channel
2. See "Channel 2 Power when using TW Power
Supplies", below.
3) Reconfigure the RM-325 for local power. See
"Supplying Local Power when Using TW Power
Supplies", below.
2.3.2.1 Channel 2 Power when using TW Power
Supplies
To power the RM-325 from channel 2, carefully and
completely cut the circuit trace between X2 pins 2&3.
Then solder a jumper between X2 pins 1&2. The RM-325
will now receive power from channel 2, and both
channels will be terminated by the TW power supply.
2.3.2.2 Supplying Local Power when Using TW
Power Supplies
To use a local power source, carefully and completely cut
the circuit trace between X2 pins 2&3, and leave all X2
pins unconnected.
Connect your own local 24 VDC power supply to the
AUX connector. (Use a well filtered power source, 60 to
100 mA.) Pin 6 is +DC. Pin 14 is Common.
The RM-325 will now receive power from the local
power supply, while both channels will be terminated by
the TW power supply. Note that since the RM-325 is not
drawing any power from the channels, you should not
include this station if you are computing total power
consumption for the TW power supply.
2.3.3 Channel Connections when using all Lo-
cally Powered Intercom Stations
There may be a few occasions where it makes sense to
locally power all of your intercom stations. For example,
your intercom stations may be widely dispersed about a
large building complex, where stations are separated by
anywhere from 1000 ft to 10,000 ft. Due to wire
resistances, it is not practical to supply power over the
intercom channels for these distances. However, the audio
and signals can operate over this range. The solution is to
supply power separately to each station.
When all stations are locally powered, and there is no TW
power supply in the system, a line termination will have to
be inserted at one (and only one) location in in each intercom
channel. It doesn't matter where, but it is important that there
is only only one termination per channel. Figure
10
RM-325 User Manual
To an Intercom Station
LINE INPUT Connector
3-Pin Male
XLR Connector
Figure 4. Termination plug for 2 intercom chan-
nels when all stations are locally powered
how to construct a termination plug for this purpose. Plug the
termination plug into the intercom LINE INPUT connector
of only 1 intercom station. Then plug a standard 2-channel
TW cable into the LINE LOOP connector to connect to
another intercom station.
2.3.4 Distributed Power from a Non-TW Power
It is possible to power several TW intercom stations from
a single, non-TW power source, such as a battery. This
might be an ideal setup for a small, portable system where
AC power is not available. This method uses channel 1
only to connect the non-TW power supply. Audio on
channel 1 will be unusable. Channel 2, however, will still
be operational. Also, channel 2 will require a terminating
impedance, since this is not supplied by the non-RTS
power supply.
Figure
connect power. Plug the power/termination plug into the
intercom LINE INPUT connector of only 1 intercom station.
Then plug a standard 2-channel TW cable into the LINE
LOOP connector to connect to another intercom station.
2.4 Program Input Connections
You can connect a balanced or unbalanced audio source
to either the PGM input connector or to the AUX
connector. Refer to the specifications (page 6) for
pin-outs of these connectors.
4
shows
{
Pin 3
Ch 2 Audio
Pin 2
Ch 1 Audio
Pin 1
Common
Resistors 200 Ohms, 1/8 Watt
Capacitors 10µ, 50V Electrolytic
2
3
WIRES MUST NOT TOUCH!
Source
5
shows how to construct a termination plug and also
200
Ohms
+
+
10µ
50V
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