102 versus 202

[poplar1]

But side-tone subsets do have an advantage in that you can connect more than one phone to them.  With anti-side-tone subsets, you can't, as you won't be able to hang up, just as if the phone in the other room was left off the hook, unless you use phones that are made for that usage.  They have an extra set of contacts.

Yes, you can hang up, because on both 202s, the Y and BK hookswitch contacts will be open.

The problem is that when either 202 is off-hook, the red and black mounting cord conductors of both 202s, which are not switched, will be live. So you can eavesdrop on the hung up 202 from the off-hook telephone.

You need a 215 (D8 handset mounting) at both locations connected to a single AST subset. The D8 does have additional R and RH contacts which complete the path from R in the subset to the transmitter through the red handset conductor, but only for the phone in use.

[TelePlay]

I had a very nice, fully functional side tone stick. Sold it. I never got use to hearing the sounds of my hand holding the stick during a conversation. Every slight shift in my hand was picked up by the transmitter and heard in the receiver, quite loudly.