ITT Semicon to BT431a - UK Vintage Radio Repair and Restoration Discussion Forum

newlite4 · 30th Jul 2025, 7:26 pm

I have an ITT Semicon Petite metal French "boudoir" style phone (ownaphone) with no bell from the mid 1980s. It uses only two wires which have been cut off from the rear. I intend to fit a salvaged BT 431a plug and cable to the phones internal connector block. Which of the two BT plug pins (2,3,4 and 5) do I connect to the phone.
Neil

Dave Moll · 30th Jul 2025, 8:01 pm

If there are only two wires, it is reasonable to assume that they would go to pins 2 and 5.

newlite4 · 30th Jul 2025, 8:44 pm

Thanks for that Dave, I had an idea that it would be 2 and 5, I had searched the web and came across lots of confusing information which threw me off the scent.
Neil

Nickthedentist · 31st Jul 2025, 1:38 pm

Yes, for two wire working, it’s the outer two of the four terminals, either way round in practice.

The very outmost of the six positions are not used in domestic installations.

newlite4 · 31st Jul 2025, 3:23 pm

Yes Nick, I think the outer two - 1 and 6 - are for data applications,
Neil

30th Jul 2025, 7:26 pm	#1
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,972	ITT Semicon to BT431a I have an ITT Semicon Petite metal French "boudoir" style phone (ownaphone) with no bell from the mid 1980s. It uses only two wires which have been cut off from the rear. I intend to fit a salvaged BT 431a plug and cable to the phones internal connector block. Which of the two BT plug pins (2,3,4 and 5) do I connect to the phone. Neil __________________ preserving the recent past, for the distant future.

30th Jul 2025, 8:01 pm	#2
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,453	Re: ITT Semicon to BT431a If there are only two wires, it is reasonable to assume that they would go to pins 2 and 5. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

30th Jul 2025, 8:44 pm	#3
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,972	Re: ITT Semicon to BT431a Thanks for that Dave, I had an idea that it would be 2 and 5, I had searched the web and came across lots of confusing information which threw me off the scent. Neil __________________ preserving the recent past, for the distant future.

31st Jul 2025, 1:38 pm	#4
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 19,242	Re: ITT Semicon to BT431a Yes, for two wire working, it’s the outer two of the four terminals, either way round in practice. The very outmost of the six positions are not used in domestic installations.

31st Jul 2025, 3:23 pm	#5
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,972	Re: ITT Semicon to BT431a Yes Nick, I think the outer two - 1 and 6 - are for data applications, Neil __________________ preserving the recent past, for the distant future.