UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

TonyDuell · 6th May 2020, 7:54 am

I seem to remember that when I worked through the Plan 105 External circuits, you do need the A leg to be earthed for the ringing circuit to be completed. It was assumed this was done at the exchange, but when I was running the setup on a line simulator on the bench it did not ring until I'd made that connection.

Of course the A leg would normally be essentially earthed at the exchange so it will work without extra connections on a normal telephone line.

6th May 2020, 7:54 am	#27
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,225	Re: Plan 105 with external extensions I seem to remember that when I worked through the Plan 105 External circuits, you do need the A leg to be earthed for the ringing circuit to be completed. It was assumed this was done at the exchange, but when I was running the setup on a line simulator on the bench it did not ring until I'd made that connection. Of course the A leg would normally be essentially earthed at the exchange so it will work without extra connections on a normal telephone line.