The figure ABC photo shows the top side of the circuit board mostly occupied by the 68HC11 processor and socket. The dual-row header across the bottom provides access to most of the processor I/O pins.
Figure 1 ABC photo
The transmitter control signals (PTT, keyed tone, ON/OFF keying) are on the
right side of the header. These signals connect with jumper wires to the 3.5mm
stereo jack on the front panel for connection to the radio. Additional jumpers
near the jack allow for configuring the controller for separate PTT, audio or
for combined audio/PTT typical of modern hand-held radios.
The serial interface pins (5V TTL levels) are on the left side of the header (but not connected in this image).
The processor operating mode jumpers are on the leftmost header pins. The jumpers are shown in the fox controller mode.
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