Banjo

It is a Accenta 396 Optima G3.

Hi I recently damaged one of the cables going from the control panel to the one of the PIRs when decorating. Through the white cable I can see it was the black cable and within that one of the strands is broken - so there is definite damage. Before I finish decorating I have an ideal opportunity to replace the damaged cable. I have run a new length of the same cable under the floor and have one end at the PIR and one end at the control panel. My intention was to power off the control panel at the consumer unit and disconnect the battery from the control. I could then replace the cable using the existing cable as reference. This doesn’t work, as soon as the battery is disconnected in the control panel the external sounder rings. Is there a way from the control panel I can disable the external sounder? If not is there an easy way to do this within the external sounder? (Equipment - Control panel: Optima G3, External sounder: Pyronix Deltabell E/Deltabell PLUS.) I would ring the original installer but with the coronavirus outbreak I can’t see I would get this sorted in the coming weeks and time is now one thing I have. Thanks for your help.