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appropriate wattage non-inductive 50 Ω resistor.
You can then easily calibrate or verify the PLC
transmitter's output power level into this 50 Ω load.
Also, a proper 50 Ω load is provided to the line
tuner so as not to disturb the impedance of the
opposite end of the line. Using this switch to isolate
the line tuner provides a quick way to verify if the
line tuner is affecting the transmit level and
reflected power. Also, it is a way to check if the
carrier set, hybrids, & wiring are affecting the
receive signal.
8.2.4 RF Signal LED
There is a RF signal bi-color LED on the front that
lights up green when the board is in test and red
when in service for the normal -001 style board.
The LED is powered by the carrier signal itself, and
its intensity varies with the carrier signal level. It
lights brightly for a 10 watt level and dimly for a 1
watt level. This is handy for a quick visual verifica-
tion that the expected carrier signal is being sent.
It's fast responding so that it shows checkback test
coded pulsing when this is used. It also shows the
TX level ramping up to 10 W when calibrating the
TX. Additionally, if a RX signal is strong enough it
will show the RX signal when the local TX is
turned off.
8.2.5 Coax Connectors (on rear)
The rear has three BNC coax ports, one for "IN1",
one for "LINE" and a third bridging port "IN2",
which is in parallel with "IN1" for connecting a
bridging piece of test equipment, like a high-Z
frequency selective level meter, when needed. This
third port also allows for bypassing the whole PLC
Test Board by moving the "LINE" coax cable over
to the "IN2" port if, in the rare case, an issue ever
arose with the PLC Test Board.
• IN1 – For input from carrier set or last hybrid
• IN2 – Normally a bridging port for test (For
RX-only units provides a connection to a
2nd RX)
• LINE – For output to line tuner
April 2023
Chapter 8. PLC Test Board
Page 8–3
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