Old GPO Office Telephone - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

TonyDuell · 19th Feb 2016, 8:23 pm

No, you connect the line to 4 and 6. (in the planset)

You connect the battery between 16 (-ve) and 20 (+ve) in the planset, although without extensions (and thus no line current in the extension circuit) I am not sure much will happen.

You really need to download the diagrams I mentioned. N625 includes a layout of the planset, and shows how the termnals are numbered.

Dave Moll · 19th Feb 2016, 10:00 pm

It's OK, if all you want the battery to do is light up the red and white lamps, this works even without an extension connected. Also the main station happily connects to line without the extension. Beware, however, that the bell in the main unit will only ring on incoming with "speak to exch" selected. When "extn to exch" is selected, the bells are wired in series, so the absence of the extension and its bell means that the bell circuit would be open. This could be circumvented by bridging the connections for the extension's bell (terminals 11 and 14) - though I haven't actually tried it.

Earlofdon · 19th Feb 2016, 10:12 pm

Thanks guys,
I'm on it right now

julie_m · 20th Feb 2016, 2:51 am

Terminal 11 - Terminal 14 would be a good place to fit the usual 3.3 kΩ resistor to decrease the REN of the old 1 kΩ bell.

Dave Moll · 20th Feb 2016, 9:33 am

Bear in mind, though, that to get the benefit of this resistor, you need to keep the "extn to exch" button operated when the planset is on-hook. You would then need to press "speak to exch" on answer - returning to "extn to exch" when clearing the call.

Earlofdon · 21st Feb 2016, 5:15 am

It works - marvellous!

Earlofdon · 21st Feb 2016, 5:17 am

And the other light!

AndiiT · 21st Feb 2016, 2:28 pm

Hi,
Apart from having the added advantage of the lamps operating the "Speak to Extension Exchange Held" button should allow you to hold a call which is in progress, should you wish to - to be fair that feature should work whether there is a power supply connected to the plan set or not.

Dave Moll mentioned about the bell not ringing if the speak to exchange key is not operated but I'm sure that the bell in my planset rang fine with all keys in the released position. I'll have to check the N diagrams when I get chance.

An extension telephone could be connected on terminals 14 and 16 of the block terminal but you would have to have some additional bits (as already mentioned) for signalling between the extension phone and planset.

Andrew

Dave Moll · 21st Feb 2016, 3:40 pm

I think it's only when "extn to exch" is pressed that the bell doesn't ring, owing to the bell in the extension being placed into circuit in series with the main in that position. Apologies if I didn't make that clear. This is my thinking about the resistor only being in circuit with this key pressed.

I must admit that I hadn't checked the "speak to extn" and "clear" states when I made the original comment.

19th Feb 2016, 8:23 pm	#21
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Old GPO Office Telephone No, you connect the line to 4 and 6. (in the planset) You connect the battery between 16 (-ve) and 20 (+ve) in the planset, although without extensions (and thus no line current in the extension circuit) I am not sure much will happen. You really need to download the diagrams I mentioned. N625 includes a layout of the planset, and shows how the termnals are numbered.

19th Feb 2016, 10:00 pm	#22
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,127	Re: Old GPO Office Telephone It's OK, if all you want the battery to do is light up the red and white lamps, this works even without an extension connected. Also the main station happily connects to line without the extension. Beware, however, that the bell in the main unit will only ring on incoming with "speak to exch" selected. When "extn to exch" is selected, the bells are wired in series, so the absence of the extension and its bell means that the bell circuit would be open. This could be circumvented by bridging the connections for the extension's bell (terminals 11 and 14) - though I haven't actually tried it. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

19th Feb 2016, 10:12 pm	#23
Earlofdon Retired Dormant Member Join Date: Feb 2016 Location: Coventry, West Midlands, UK. Posts: 13	Re: Old GPO Office Telephone Thanks guys, I'm on it right now

20th Feb 2016, 2:51 am	#24
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Old GPO Office Telephone Terminal 11 - Terminal 14 would be a good place to fit the usual 3.3 kΩ resistor to decrease the REN of the old 1 kΩ bell. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

20th Feb 2016, 9:33 am	#25
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,127	Re: Old GPO Office Telephone Bear in mind, though, that to get the benefit of this resistor, you need to keep the "extn to exch" button operated when the planset is on-hook. You would then need to press "speak to exch" on answer - returning to "extn to exch" when clearing the call. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

21st Feb 2016, 5:15 am	#26
Earlofdon Retired Dormant Member Join Date: Feb 2016 Location: Coventry, West Midlands, UK. Posts: 13	Re: Old GPO Office Telephone It works - marvellous! Attached Thumbnails

21st Feb 2016, 5:17 am	#27
Earlofdon Retired Dormant Member Join Date: Feb 2016 Location: Coventry, West Midlands, UK. Posts: 13	Re: Old GPO Office Telephone And the other light! Attached Thumbnails

21st Feb 2016, 2:28 pm	#28
AndiiT Octode Join Date: Aug 2005 Location: Saltburn-East, Cleveland, UK. Posts: 1,786	Re: Old GPO Office Telephone Hi, Apart from having the added advantage of the lamps operating the "Speak to Extension Exchange Held" button should allow you to hold a call which is in progress, should you wish to - to be fair that feature should work whether there is a power supply connected to the plan set or not. Dave Moll mentioned about the bell not ringing if the speak to exchange key is not operated but I'm sure that the bell in my planset rang fine with all keys in the released position. I'll have to check the N diagrams when I get chance. An extension telephone could be connected on terminals 14 and 16 of the block terminal but you would have to have some additional bits (as already mentioned) for signalling between the extension phone and planset. Andrew

21st Feb 2016, 3:40 pm	#29
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,127	Re: Old GPO Office Telephone I think it's only when "extn to exch" is pressed that the bell doesn't ring, owing to the bell in the extension being placed into circuit in series with the main in that position. Apologies if I didn't make that clear. This is my thinking about the resistor only being in circuit with this key pressed. I must admit that I hadn't checked the "speak to extn" and "clear" states when I made the original comment. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)