Remote Control Console
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7. PLM Description
7.1 INTRODUCTION/DEFAULTS
The Phone Line Module (PLM) for the C-6124 system provides telephone communication over a PSTN line.
7.2 INPUT/OUTPUT
Two jacks are available for external access. The recorder jack is a 3.5mm female plug. The line jack is an FCC
approved RJ-11 standard modular jack.
7.2.1 LINE JACK
The line interface of the PLM is a four-position/two conductor modular connector. A six-foot cable is
included with each card for use as is appropriate.
7.2.2 RECORDER OUTPUT
The recorder jack is a 3.5 mm female audio jack. This output provides both transmit and receive audio as
heard by the single PLM. The output is 600 ohm balanced. The receive path audio is always included in the
recorder output. Two jumper selections allow the user to select if the transmit side contains tones and if
crosspatch transmit audio is to be included. See section 7.3.3 for a complete description.
7.3 STANDARD OPERATION
Two modes of operation are available with the PLM/DLM. The first is as a standard telephone card and the
second is as a dial-up line.
7.3.1 PHONE LINE MODULE (PLM)
Placing JP1 in the B position configures the card for telephone mode. In this configuration, the card will act
as a standard telephone.
7.3.2 DIAL-UP LINE MODULE (DLM)
Placing JP1 in the A position configures the card to act as a dial-up module. JP7 must be in the A position.
This introduces control tones into the system, which are used by a remote adapter to directly interface with
a radio. This mode allows remote radio control without having to lease a line. This mode requires a Vega
RP-251 remote adapter panel to work with. A positive keying tone gives security against outsiders calling
the remote number by mistake.
7.3.3 RECORDER OUTPUT
Receive audio to the recorder is taken after the receive notch filter. This removes any keying tones that may
be present during DLM mode. As the hybrid isolation is not high, transmit audio is present in the receive
path as well. Because of this, both the receive and transmit audios may be recorded using just the receive
path.
JP14 and JP15 are added for test purposes. Since all audio is found on the receive path neither of the
transmit audio paths available should be summed into the recorder circuit. The jumper plug for JP14 should
be removed and JP15 should be in the B position.
7.3.4 SQUELCH CONTROL (DLM mode only)
Squelch control allows the system operator to set up the receive path so the receive bus will not be driven
unless there is a minimum audio level on the receive path. The squelch control disables the audio gates
until the LAM circuitry activates. The receive gate will allow RX audio through only as long as the audio
maintains a minimum audio level as judged by the LAM circuit. There are three receive audio paths – Select,
Unselect, and Crosspatch RX. Each may be configured with squelch control independently.
Description
Jumper
Position
Select squelch enabled
JP4
B
Select squelch disabled
JP4
A
Unselect squelch enabled
JP3
B
Unselect squelch disabled
JP3
A
