NGT—Technical description (2010)
100 NGT Transceiver System Technical Service Manual
Filter and Control PCB
IC2 is in Sleep mode when no data is present. When data is received from Application
Processor IC4, the RC oscillator starts to run and ‘wakes up’ IC2.
IC2 then selects the correct filter for the channel in use, the PTT switching, high/low
power switching, fast/slow ALC time constant, average ALC on/off and fan control.
Also, in conjunction with R19, IC2 forms a DAC that produces the reference ALC
voltage. This is used to control the power versus frequency output level.
Desk console
The desk console sends data via a 10-way ribbon cable to the junction box to provide
four programmed functions, F1 to F4 and PTT.
When the PTT button on the console is pressed, the goose-neck microphone (B1)
becomes active. The audio is amplified by IC2A and then passed to the junction box. V4
provides debouncing for the PTT function.
IC1 reads the data sent from the function keys, F1 to F4 and PTT. The I
2
C output from
IC1 is passed to the junction box to perform the function required.
ALTERNATIVE TEXT
Drawing 04-03169, or
Drawing 04-03369, or
Drawing 04-03542
Drawing 04-03110
NOTE
When headphones are connected to the desk console, the internal speaker
is disconnected.
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