What to check

Check the ringer volume has not been turned right down or the mute button pressed, the volume control is a spindle on the top left corner for handset/portrait types, and right top corner for landscape types.

The speaker also does incoming speech.

Corrective Action

Replace phone pcb with same type.

Links

https://www.entryphone.co.uk/shop/productdetail/PCB-500-V

https://www.entryphone.co.uk/shop/productdetail/PCB-500-PTS

https://www.entryphone.co.uk/shop/productdetail/PCB-500-PTSP