Hi,
Operating frequency switch, of the SNR.
It has 3 settings.
down - Lambda-I, frequency no.1 (It is the default [peacetime] setting, the cover used to be sealed.)
middle - Lambda-II, frequency no.2 (It is the wartime setting, can be switched only when the seal is broken.)
up - AVT., automatic frequency change between no.1 and no.2, in random time, to confuse jammers.
At the right side of the desk, there is two green lamps, indicating the current frequency.
Br,
Hpasp