The V50 control unit controls only the V50 phone

No other phone shares the same control protocol as the V50.

Remember: not only do you have Microphone and Speaker connections, there's also the control to make/end a phone call, dial numbers, etc etc. This control varies hugely from phone to phone.

If you wish to have universal control capability, where the control unit can control many different phones, then you need to use the ULF or the TCU-BT (new version TCU that has Vluetooth built in) control unit, and connect the phone via Bluetooth. It's the only way.