The dual crystal switch was used in a DC40 which uses only one frequency determining crystal. I did another one that switched 5 crystals and included a variable as a simple VXO.
Easy to do with only one crystal to switch. A little more difficult with two crystals as in the Rock-Mites. And not practical in rigs like the pig rig with 3 filter crystals on about the same frequency as TX/RX.
Chuck Carpenter, W5USJ
EM22cv, Rains Co. TX