Stuart Longland wrote:
On 03/08/14 11:10, Michael Black wrote:
The circuits of such devices were often very cleverly designed, re-using
many components between receive and transmit (using a multipole switch).

They were really complicated switches, for the sake of a few transistors.

Yep. This one I gutted, I recall de-soldering the switch and then
reverse-engineering the pinout so I could replace it with a relay, which
I did. A 4-pole double-throw relay IIRC.

Not only that the switch has many poles, the circuit is often very tricky.
It is not a receiver and a transmitter with a switch to toggle the
power, antenna and speaker/mike to connect to one of them, no it is
a blob of electronics that morphs between being a transmitter and being
a receiver when the PTT switch is switched over.

In those days I sometimes tried drawing the schematic by looking at the
PCB traces and components, and it is very difficult to draw a schematic
that makes any sense...

It is completely contrary to the electronics world today, where one would
prefer having a thousand extra transistors to save a single mechanical
component (like an extra pole on the switch). The times have changed...