I have been an NEC/NITSUKO technicial for 12 years and I have not run into this problem before, I have a customer that has a 124i system and I expanded the unit to 3 cabinets to allow for more digital extensions. With the 3rd cabinet the extensions work fine except when you press the SPK button the call1 key lights up but you do not hear an intercom dial tone.

If you then press 9 for a line out then you get a dial tone and are able to make a HF call. The phone works fine otherwise. You are unable to have voice announce calls at this extension because the speaker phone does not work.

They are using 48 digital stations and are wanting to expand.

I have tried the 92XXX and 93XXX series of phones to see if it make a change.