old retro phone conversions

[markymark2406]

I have obtained 2 old style telephones as follows:

http://andila.co.uk/retrophoneelectricblueblack-p-1230.html

They come from an office they have a wire with no plug on the end, i just need to know how i can convert to use today?

 

[Infidel]

The link you posted was for ready converted phones, if you want to convert them yourself find out what sort they are (look on the bottom of the phone it will say tele 706/746 or similar date of manufacture )
Then look them up on here
http://www.britishtelephones.com/pstconv1.htm

 

[TicklyT]

I believe loop/dis (rotary dial) signalling is possible, but now deprecated (I bet it won't be long until you end up phoning somewhere to be greeted with the recorded announcement 'Please press the '#' key to continue' )

Loop / dis dialling usually requires the third wire in telephone sockets to be connected through all the sockets, leading to problems with ADSL installations, as the connection is often isolated by the filters.

 

[Infidel]

Loop dis dialing out is not the problem, you need the third wire to get them to ring.

 

[Paul_C]

If you have a single DSL filter at the NTE, then running the rest of the phone extensions the 3-wire method won't be an issue.

Or as the 706 & 746 phones already have a capacitor inside (as they predate the current plug & jack arrangement), it's quite possible to strap them to work with a basic 2-wire connection and use the internal capacitor. You might find the bell tapping if you pulse-dial from another phone though, and it's possible that some other phones will give little taps (or chirps/clicks) when you dial on the 706/746.

There is also the REN issue, although it depends upon what phones you actually have. The original 706 & 746 models had a 1000-ohm ringer, whereas the 8746 (modified 746 put into service during the PO/BT changeover era) had a high-impedance 4000-ohm ringer. Some original 746's were converted later on.

As well as the possible need to move some straps around internally to sort out the ringing, if these phones came out of an office it's possible they also had some other wiring changes from the standard 700-series arrangement for use on a PBX system.

Basically, unless something has been drastically changed internally, if you put white & red to the A & B side of the line, you should be able to get a dialtone and dial out. The other connections will depend upon what's already there. If you can get some detailed enough photos of the wiring to the boards inside, we might be able to see what's what.

(For Tele. 706 just undo the two screws on the metal tabs in the handset cradle and the cover should lift up from the rear; for the 746 there's just a single screw at the back, above where the cords enter, then the case lifts up the same way. Be careful of the dial as you remove the cover.)

 

[TicklyT]

Loop dis dialing out is not the problem, you need the third wire to get them to ring.

Never heard of bell tinkle then!

Some equipment used to interpret 10 pps dial pulses as an incoming ring unless the bell wire was shunted by the phone sending the pulses. That problem disappeared with the adoption of DTMF signalling, making the continuous bell wire redundant.

Since ADSL was marketed after the widespread adoption of DTMF signalling, the fillter design was not made fully compatible with the requirements of loop / dis dialing. introducing ADSL filters effectively breaks the connection of the bell wire, each filter containing it's own discrete bell circuit.

706 or 746's had a REN value of 4. 8746's with a high impedance bell coil had a REN value of 1.
The issue of the bell impedance is sometimes addressed by connecting a 3K or 3.3K resistor in series with the bell coils of phones with a low impedance bell.

 

[Infidel]

Some equipment used to interpret 10 pps dial pulses as an incoming ring unless the bell wire was shunted by the phone sending the pulses. That problem disappeared with the adoption of DTMF signalling, making the continuous bell wire redundant.

Only if you still retained the old 500 ohm bell coils and converted to pst then the 3k shunt.

As well as the possible need to move some straps around internally to sort out the ringing, if these phones came out of an office it's possible they also had some other wiring changes from the standard 700-series arrangement for use on a PBX system.

The only difference will be a button on top of the phone via a clip in (switch 3a/4a If I remember ) for earth recall which can be removed you won't need it.
Got about 20 to 30 706/746 sitting in the garage and a couple of trimphones.

 

[TicklyT]

Some equipment used to interpret 10 pps dial pulses as an incoming ring unless the bell wire was shunted by the phone sending the pulses. That problem disappeared with the adoption of DTMF signalling, making the continuous bell wire redundant.

Only if you still retained the old 500 ohm bell coils and converted to pst then the 3k shunt.

The 3K resistor is connected in series with the bell circuit, not the bell shunt. misplacing it in the bell shunt circuit would prevent the shunt working effectively, leaving you with both a high REN number and a bell tinkle problem.

A correctly modified phone maintains the bell shunt circuit via both gravity switch springsets and dial springset D1 & D2.

As well as the possible need to move some straps around internally to sort out the ringing, if these phones came out of an office it's possible they also had some other wiring changes from the standard 700-series arrangement for use on a PBX system.

The only difference will be a button on top of the phone via a clip in (switch 3a/4a If I remember ) for earth recall which can be removed you won't need it.
Got about 20 to 30 706/746 sitting in the garage and a couple of trimphones.

Phones modified to N846 Fig. 2 for shared service working, which was very common in the 1970's, have the bell shunt disconnected. leaving the added thermistor in circuit could also lead to some odd behaviour of both the phone bell, and other ringers in the circuit.

At first glance, phones wired to N846 Fig. 2 could be mistaken for ones wired to Fig. 4, for 4-wire PMBX working. The same auxiliay switches are fitted, but fulfilling different functions.

 

[Infidel]

Phones modified to N846 Fig. 2 for shared service working, which was very common in the 1970's, have the bell shunt disconnected. leaving the added thermistor in circuit could also lead to some odd behaviour of both the phone bell, and other ringers in the circuit.

Nothing to do with shared service the op mentioned coming out of an office you mentioned pabx which all had earth recall buttons on the top of the instrument, or maybe a bell on off switch 3a split with earth recall or perhaps the external extension off a plan 107 who knows until we see a picture?
N diagrams got all my old ones but if you want some the most popular are here.
http://www.samhallas.co.uk/repository/n_diagrams/popular.htm

 

[squowse]

sorry to hijack, there seem to be some people who may be able to help me.
i am trying to understand the wiring connections for old phones and in particular the ringer to fix a small "problem".
i bought a fully converted old dial phone. it works fine but will vibrate like the start of a ring occasionally due to the broadband. i suppose it may be when the broadband reconnects as it drops out occasionally.
my master socket has been replaced with one of these - http://www.adslnation.com/products/xte2005.php (which i can recommend for increased speed by the way)
the phone doesn't ring unless it's plugged through a microfilter which seems to put the ring back on to the bell wire?
i wonder if there is anyway to get rid of the occasional vibration. i want to keep the phone ringing (when there is a call) as it is good and loud.