Old phone restoration

[mtt.tr]

That's the same as bulbs for Lovo lamps. Purely out of interest, how many amps could a BT cable supply?

Hardly any. The wire is at best good for a few watts. You'll blow the exchange fuse and look silly

 

[123hotchef]

That's the same as bulbs for Lovo lamps. Purely out of interest, how many amps could a BT cable supply?

looking at the thickness of it not much!

 

[123hotchef]

Hardly any. The wire is at best good for a few watts. You'll blow the exchange fuse and look silly

not if he hides the lamp quickly!

 

[rtbcomp]

I think I measured it at 48V a while back

Nominal 50 then.

That's the same as bulbs for Lovo lamps. Purely out of interest, how many amps could a BT cable supply?

Again this site might help http://www.samhallas.co.uk/telecomms.htm. IIRC the voltage can reverse under some conditions.

 

[123hotchef]

i read i can not make another main box as there will be no tone on the second phone!

so I shall have to run another from the main box

 

[cheb]

Nominal 50 then.



Again this site might help http://www.samhallas.co.uk/telecomms.htm. IIRC the voltage can reverse under some conditions.

That rules out festoon LEDs in series then.

 

[123hotchef]

That rules out festoon LEDs in series then.

will be ok with a resistor

 

[123hotchef]

It's ready to be wired up

 

[CoValent]

Again this site might help http://www.samhallas.co.uk/telecomms.htm. IIRC the voltage can reverse under some conditions.

Wow, that's an interesting site.

IIRC the ring voltage was originally 50V AC, reduced later to 48V nominal to comply with SELV limits. The line switches to DC once it is "seized" by the "instrument" to use the arcane language of the telephone lads.

BTW, regarding the lighting of LEDs from a line, yes it's technically possible by using either a bridge rectifier or two strings of LEDs in anti-parallel. However, be advised that there is well established case law for the criminal prosecution of "theft of electricity" from telephone lines. That's the mechanism used to convict the earliest phone system hackers, a practice which was known as phreaking.

https://www.bbc.co.uk/sounds/play/b08hlnjq

 

[AdrianH]

I seem to remember on the old phones that the two wires came in and went to pins 2 and 5 on the master socket. The master then had a third contact formed with a capacitor and resistor to form the bell circuit on pin 3.

Then three wires went around the house to extensions and pin 3 provided the ring volts to make them tinkle!

With modern phones they do not use pin 3 as they are such high impedance they do not need it but I would have thought if you can plug the phone into the master socket, i.e where it comes into the house it may have a better chance to ring then on an extension socket. If it rings on that socket then you know you need a third wire.

Adrian

 

[AdrianH]

This may be of help
http://www.wppltd.demon.co.uk/WPP/Wiring/UK_telephone/uk_telephone.html

 

[ajlelectronics]

With modern phones they do not use pin 3 as they are such high impedance

Nothing to do with impedance and everything to do with how they are wired. All older conventional telephones required the third wire because that was the connection into the ring circuit of it. It was done that way so that bells could be wired in series for bell tinkle suppression. Cordless and modern telephones pick up their own ring signal off the line.

 

[slim_boy_fat]

"Aye, Janet"

 

[123hotchef]

http://www.historyofphonephreaking.org/faq.php

Nothing to do with impedance and everything to do with how they are wired. All older conventional telephones required the third wire because that was the connection into the ring circuit of it. It was done that way so that bells could be wired in series for bell tinkle suppression. Cordless and modern telephones pick up their own ring signal off the line.

and most re pluged into the mains!

 

[123hotchef]

I seem to remember on the old phones that the two wires came in and went to pins 2 and 5 on the master socket. The master then had a third contact formed with a capacitor and resistor to form the bell circuit on pin 3.

Then three wires went around the house to extensions and pin 3 provided the ring volts to make them tinkle!

With modern phones they do not use pin 3 as they are such high impedance they do not need it but I would have thought if you can plug the phone into the master socket, i.e where it comes into the house it may have a better chance to ring then on an extension socket. If it rings on that socket then you know you need a third wire.

Adrian

i need to wire the new socket as an extension for 2 reasons one for the new bell to function right and two so that I do not loose the dialing tone on the other phones in the house

 

[ChrisW8]

Standing Phone line voltage is -50v DC.
Changes to 75v AC when incoming ringing.

 

[123hotchef]

Standing Phone line voltage is -50v DC.
Changes to 75v AC when incoming ringing.

r u sure?!

 

[ajlelectronics]

r u sure?!

He is quite correct.

 

[123hotchef]

wow how does it know?
does that happen at the exchange

 

[123hotchef]

i am just waiting on the bell then I can have a play, the phone is ready to go the new socket and cable turned up today shame the socket is a screw type as i really wanted to use the punch tool aint used it for years