Hitachi 'sleep' Function

Hi

I have recently acquired a TRK-7250E and I am unsure on the functionality behind a couple of switches.

What does the 'Sleep' function do? / how does it work?

Also what does AFC do? - can this be left on?

Stereo / Mono - can this be left in Stereo?

I am asking because I am planning to mod by box and might repurpose these switches.

Many thanks

K

Sleep mode is to allow the radio to switch itself off using a tape as the timer, so a C90 gives you 45 minutes of snooze time, a C120 an hour and so on.
AFC is to reduce drifting off stations on the VHF/FM band, it is best to leave it off if you listen mostly to distant stations as otherwise, it tunes to the stronger signal on that channel and ignores the lower powered one. So use of AFC depends on whether you mostly listen to distant stations or local ones. AFC is often offered alongside a local/DX switch to adjust the set's sensitivity for that purpose.
Stereo/mono FM is better in stereo but for weaker stations leave it on mono as this will reduce background hash and make for clearer reception.

Many thanks Beosystem10