He is not much of a tech if he doesn't know what those switches are for.
What the switch does is marked right on the radio itself, Geez!
If you don't know, then here it is.
The RX/TX - RX switch determines the function of the coarse ( big knob) clarifier to shift the frequency of both the transmit and receive frequency simultaneously when the RX/TX is selected. This lets you "slide" between channels like transmitting and receiving on 27.400 MHz.
When RX is selected, then only the received frequency is shifted with the coarse knob and usually used to clarify off frequency stations. This does the same as the inner small knob but with a wider range of adjustment. These knobs are primarily used in SSB mode.
The off button is just that, the clarifier is out of the circuit .
The small knob fine clarifier is for receive only unless some idiot modified it and it's used only for small fine receiver adjustments and in most cases, is usually good enough to tune in off frequency SSB stations.This knob can be used independently on either side of the RX/TX - RX switch.