I owned the Icom IC-22S, when they were new in mid-1970s.
It shares many case parts with the IC-22A, which was a 22 channel crystal controlled radio.
The factory version of the IC-22S used a 23 position knob, which was numbered 1-22 with the 23rd blank, as I remember. The frequencies for each of these channel positions was programmed (diode matrix) with 1N914/1N4148 silicon high-speed diodes.
Now, digital technology was progressing rapidly in this time period -- and a number of third-party modification kits (in USA) were offered to expand upon or change how this diode matrix scheme worked.
Some of these kits changed the channel switch and indicator to more than 23 positions.
These switches, 23 and 40 position, were very cheap in late 1970s -- due to end of 1970s CB craze and large parts surplus.
There were several -- you would have to read the magazines advertisements of that period -- to see all the different versions or try to find out what you have, IF no documentation was provided by former owner.
Last edited by W9GB; 04-09-2012 at 03:42 AM.
We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths. -- Walt Disney