I have one of these phones, and the flash button came pre-programmed to break the line connection for 600 msec when pushed. This is simply too long for the CO I used. The line winds up getting dropped.
The thing seems imminently programmable, but I haven't been able to figure out how to shorten the flash time. This phone is no longer sold by IBM, but is sold as the Cortelco 4125. I called them and asked, but they say they only know how to program the newer model.
I would imagine that the old board is programmable, too, but no-one bothered to document it. I keep trying to find the manufacturer, but no-one will confess. The distributor for the US, TT Systems, seems to have ceased operations.
Any pointers or tips would be really useful.
Thanks,
Charles Buckley