Batboard

Hi
I have another question I cannot find in any operators manual or service manual I have. That shows it. Have R2200A manual from Motorola Hard Copy.
There is a BNC connector and switch one the rear of the R2200B service monitor looking at the rear it's on the right side other side from fan, that I find no reference to.
Can someone help an old guy out what is it? What's it for and do.
Thanks for any information.

My guess it is for going between internal oscillator and an external 10 meg oscillator.

probably someone added an ext 10Mhz input with a switch to toggle between internal and external.

Just a guess though but that's where the internal 10Mhz reference is located

Thanks I had never seen the BNC before on any info or manuals, my buddy just got 2 off of bay and they both have bnc connector and switch on rear. Both are in need of LVPS repairs.
Thanks again for the info. Guess if they don't come up will have to try the switch in other position, it's not marked.