Front Panel Controls - Codan X-2 Service Manual

Technical Description 4-14
4.5.4

Front Panel Controls

104-02909
The front panel has the following controls:
Channel Change
A continuous rotatable 12 position switch provides a Gray code on its four
outputs and is connected to IC1 pins 9 to 12. Channel selections are read by
the microcontroller via the I
VCO2 according to the information stored in the EEPROM. Only 10 of the
12 positions are used.
Clarifier
A continuous rotatable 12 position switch provides a Gray code on its four
outputs and is connected to IC1 pins 4 to 7. Any position change in the
receive mode is read by the microcontroller via the I
The microcontroller adjusts VCO2 in 10 Hz steps to a limit depending on the
channel frequency. The clarifier automatically resets to mid frequency when
the channel is changed.
Emergency Call
A biased toggle switch provides a ground to pin 28 of microcontroller
IC403. If enabled on the selected channel, the microcontroller selects the
PTT function and outputs the two emergency tones of 880 Hz and 1320 Hz
from pins 1 and 2. Modulator IC301 receives these signals via the
microphone amplifier.
USB/LSB
A two position toggle switch provides the selection of USB or LSB by a
high or low applied to pin 30 of microcontroller IC403. The microcontroller
selects the appropriate local oscillator (applied to the
modulator/demodulator).
The selection of USB and LSB is only available when enabled for the channel
selected.
Tune/Mute Off/Mute On
A three position toggle switch, biased up for Tune select and selectable for
Mute On/Mute Off.
When Tune is selected, a ground is applied to pin 32 of microcontroller
IC403. This selects transmit mode and injects the carrier via IC14/A and
V13 into the transmit path of the exciter.
When Mute On is selected, a ground is applied to pin 29 of microcontroller
IC403. The microcontroller changes mute control line from IC308/D pin 13
to operate the mute gate IC305/A.
Power On
The power on switch is part of the volume control assembly. When the
contacts are closed, relay K8 is energised on the PA PCB and provides the
DC supply to the transceiver via contacts K8-1.
2
C bus. The microcontroller sets up VCO1 and
X-2 Technical Service Manual
2
C bus.
Publication No: 15-02047