Batboard

…while it does on GP1200.

Is this a programming issue I can correct or do I have no chance to get this to work?

Strange thing, isn't it?

Allright - I tested a standard NMN6191B on the MT2100 in question and it doesn't work either.
I also figured the MT2100 was a GP1200 once and is, unlike the other GPs, a 7AN model instead of a 7BN.
Are there any known issues using speaker mikes on early GP1200s or did I just score a wrecked one off eBay?