Okay, here's what I did:

Set the bits on command 100 to 082223161.

From what I read in the manual, command 100, register 08 is the overflow control. I don't think this is really what we want. Here's why I think that:

When an outside line calls in, the console rings for 20 seconds, then goes into overflow, which then forwards to group 161. This is fine except it sets the overflow mode to on, and all subsequent calls drop straight to group 161. When you push the overflow button on the console, you have taken it out of overflow mode, and it works fine for the first unanswered incoming call.

What is desired is a busy/noanswer forward to group 161 that doesn't require the operator to reset the overflow mode each time. Or can the overflow mode be automatically reset each time or after a timeout?