Mark,

When I tried the default FS command a second set of beepings started (different pitch) which makes me think the NAV ID are encoded in the CS707 radio gauges.

Anyway, I found out the correct switches: the ones marked RANGE on the audio panel, just below the radios. If I click them more than once the beeping stops. BTW, there's a typo in the numbering used to identify the switches in the manual (vol. 2).