238L / Bellset 33 on a modern line?

[pyoor]

Hi folks,

I've finally managed to dig out my 238L / Bell set 33 (I think it's a 33 - see photos) which I'd like to hook up to our phone line in addition to our current 312. Ideally, I'd like it wired up so the pay-on-answer mechanism is still functioning.

(Many) years ago, my dad and I had a brief look at the problem, and got as far as everything but pay-on-answer working (so you could dial, hear the person, but not speak to them).

Does anyone have any links that might be handy for sorting out the wiring. I've spent some time on google (and searching on here) but couldn't find anything relating to bellset 33 - which I'm thinking is what I've got.

I got as far as this: http://www.britishtelephones.com/bellst33.htm

But couldn't see any information on wiring the wee beastie.

Any advice'd be gratefully received.

Incidentally, the 'final' plan is to stick a VOIP box in front of it, so suggestions on neatly and reversibly hiding a tone-dial device would also be handy (I've got a BT tone-dial box, but it only sort-of-works with the 300 series phone (press and hold the tone then wave it around until it happens to catch the sound)).

Thanks!

[dagskarlsen]

This was a difficult one.

I'm sure this is not right, but it will probably work, until someone got so angry over this way to solve it, that they comes with the right way to do it.

It will probably dial well with a dialgizmo plugged into your ATA.

T2-2
T7-5
T8-14
T9-T1 and 1
T6-4

The line goes to
2 and 15.

Good luck

dsk

[pyoor]

Excellent! Thank you so much. I'll try it out (tomorrow I hope) - and let you all know how it goes.

[pyoor]

Hiya,

No luck so far. I've used the white and red from the line cord as A and B wire (I think that's right, yes?).

Connecting the phone leads immediately to the handset appearing to be picked up, although the handset is disconnected until you pick it up. Dialling does not work (whether I pay or not!).

Connecting the phone whilst ringing our landline (obviously) leads to immediate connection, but allows me to say that:

Speech from the phone - fine (although there's some echo into the 238L's handset. Not sure if that's a fault with the phone, we have a pretty lousy line).
Speech in from the testing telephone (my mobile!) - not heard.

Payment makes no difference.

Prior to connection I checked, and the telephone (238L) is wired as here: http://www.samhallas.co.uk/repositor.../0000/N338.pdf

In terms of the bellset/payphone box, the links are still in place between 11, 12 and 13 (actually I had to replace the link because it was missing on 11-12). 14 and 15 are also linked now linked (they'd been disconnected by moving the link bar, but the bar was still present).

Looking at the telephone itself I'm not sure how it was originally connected to the telephone network. The number indicated is 01-730 - and I know it came from Imperial College. I'm assuming it was originally connected to the BT-run telephone exchange, (http://www2.imperial.ac.uk/blog/vide...e-system-1984/) although I'm somewhat confused by the number - and the fact I know it must have been removed in the early 1960s (because my dad got it when it was removed, whilst he was at university, to be replaced with 705s). I would have imagined that there were more than 730 phones in the 01 dialing code area when it was introduced, but I don't know that much about the history of the phone system... But my understanding of the Imperial College phone system is there wouldn't have been much point having a payphone on the internal system.

Any further suggestions for the 238L/33 combo would be gratefully received.

Minor moment of pointless nostaligia: I once went to retrieve a 705 that had been vandalised and thrown in a stream near my flat in Birmingham, sadly the day before I went, they dredged all the rubbish from the stream... mind you, I don't really need more phones.

[dagskarlsen]

OK The hybrid in your bell-set is rather complicated.

If we start with basic telephony theory the simplest possible dial telephone is the one on this picture. The reasons for not using this are mainly 2:
1: after the times goes, the permanent magnet in the receiver looses magnetism, and "dies" (many hours of use)
2: The side-tone (hearing you selves) are far to strong, then you automatically lower your voice and the other end "cant hear you".

How does it work?
Follow red: Line comes in T2 hook sw. 3-4 allows current to pass when off hook. The dial pulse switch 5-4 sends pulses when dial returns. Else the current just goes further to transmitter and receiver end out back to the line.
The green circuit 4-3 shorts the receiver and transmitter when dial is out of res position, this is mainly to save your ears from loud clicking when the dial returns.

dsk

[dagskarlsen]

I got the the solution.
Dug out results: the diagram under.

Since you probably don't have the coin box system we skip that and connects as in the diagram with some colors.

The colors are just to make it easier to follow.
Red and green ends up at telephone line (ATA)

Good luck.

dsk

[pyoor]

Thanks! Unfortunately it's still not quite there. Connecting the phone still leads to an immediate off-hook state. However I can now both hear incoming voice and outgoing speech. The dial clicks audibly on the earpiece, but doesn't have any effect on actually dialling - which I suspect is related to the off-hook issue...

Third time lucky?

Thank you all for putting such effort into this!

[pyoor]

Having nosed at faultfinding - and having noticed that I didn't mention something, here's a bit more info re the fault:

Whilst the phone appears to be off-hook, the actual handset *is* disconnected.

Also, this iteration of the wiring, the speech is noticably poorer than it was before.

Uhm, so, yes, any more suggestions would be gratefully received.

[dagskarlsen]

I really like to do this, it makes me understand the circuits better.

Here, i have a feeling about the map doesn't match the terrain, so we have to do something

If
1) the capacitor is defect, and leaks DC, it has to be changed.
(are you able to test it with e.g. an ohm meter?)
2) The hook-switch between T2 and T3 doesn't open when going on hook it has to be adjusted.

Then if OK; start again wiring the line to the B2 & B14 (nothing else) it shall not go off hook, and the ringer shall ring when you try to call, e.g. from your mobile.
(If this works, the capacitor should be OK)

Putting in the 2 wires Red/Blue the telephone shold stop the ringing when going off hook, and the other end should hear you, but you hear nothing.
You should also be able to go off hook, and dial. your mobile, and it should ring.

Connecting the red green wire, and you should hear something maybe weak.
Still able to go on and off hook.

Loud! clicks when dialing.

Connecting green/yellow, and the clicks should (almost) disappear.

If dialing has worked until now, but stops working OK, try to swap wires from dial connected to T3 & T4.

If it works reasonably by now the yellow wire T5 & B4 should make the sound stronger in your receiver.

Test dialing, and ringing.

The last yellow T9 & B8 should just reduce clicking when dialing even more.

Please do this step by step, and stop when it fails.


dsk

[Pellseinydd]

Hi
The diagram that you need to connect you Tele 238 to the Bellset 33 is N2408 which can be found at
http://www.samhallas.co.uk/repositor...2000/N2408.pdf

A few questions?
Is the Tele 238 fitted with a Dial No 11 or No 13 ('coinbox dials with the extra contacts)? Sometimes over the years they have been altered to non-coi8nbox dials.
Are you using the original thick eight core rubber covered cable between the Bellset terminal strip and the telephone? If so check the colours correspond to those on the diagram.

One thing to note is that the coinbox set up is not known as a 'Pay on Answer' telephone but a 'Pre-payment' telephone. i.e. you had to put the correct number of coins in before a short circuit was taken from across the dial pulsing contacts(contacts BA) . At the same time another pair of contacts short circuited the transmitter so it was ineffective until either Button A or Button B was pressed. It also degraded the received speech to prevent people shouting into the reciever to speak without pressing Button A if the call was successful. Self dialled calls on these telephones were limited to local calls - trunk calls were via the operator - dialling the '0' (or 100 just before STD in some areas) didn't short the mic/receiver.

The 'Pay on Answer' coinbox introduced for STD in 1959 were the Telephones 705/725/735 where it was possible to dial on lifting the handset and when the called number answered, a series pips was received and then you inserted the money rfor the call. During the call, when your time was nearly up you received more pips to put more money in.

I've got a number of these A/B boxes - going as early as 1927 - the one in the picture at http://www.britishtelephones.com/t123.htm is mine.

I worked on these coinboxs back around 1960/61 in my GPO days !

[Pellseinydd]

Originally Posted by pyoor

Looking at the telephone itself I'm not sure how it was originally connected to the telephone network. The number indicated is 01-730 - and I know it came from Imperial College. I'm assuming it was originally connected to the BT-run telephone exchange, (http://www2.imperial.ac.uk/blog/vide...e-system-1984/) although I'm somewhat confused by the number - and the fact I know it must have been removed in the early 1960s (because my dad got it when it was removed, whilst he was at university, to be replaced with 705s). I would have imagined that there were more than 730 phones in the 01 dialing code area when it was introduced, but I don't know that much about the history of the phone system... But my understanding of the Imperial College phone system is there wouldn't have been much point having a payphone on the internal system.

01-730 was STD code for Sloane exchange in the London 'Director' area and the telephone would have had a four digit number off Sloane exchange. The A/B payphone would have been on a 'Direct Exchange Line' - very unlikely that it was via the switchboard and would not have been on the internal automatic system.

However Imperial College's telephone number was on Kensington exchange (KEN 5111) in 1963 - the last year that A/B boxes would have been used prior to the introduction of STD by end of March 1964. Once London went over to all figure numbers 1966/67 it became an 01-589 (South Kensington exchange number) and at the same time some of the student houses are shown as having 01-370 numbers (Earls Court exchange) which came into existence at that time.

Is it an 01-730 xxxx number on the dial label or was it a 'typo' for 01-370?

[pyoor]

Sorry for the slow reply - I've been away on holiday and then been ill!

So to cut a long story short, it's now working. I wired it according to the diagram from Pellseinydd - and it does indeed work exactly as 'it says on the tin'. It is now hooked up as a Pay-On-Answer payphone, with the coin drawer open so people can use it, and it cheerfully rings... properly. None of this nonsense trilling or playing dancie tunes.

For those interested, the process was possibly slightly indirect:

- The Capacitor is indeed be working. Checking it with an ohm-meter, it briefly flicks towards 0 ohms before heading back towards infinite resistance and stopping there.

- T2/T3 / the hook switch was tested and found to be working as expected.

- Disconnecting the 'phone completely (all 8 wires of the black cable that runs to the phone) (I'm assuming that's what you were meaning) and connecting line to B2 and B14 led to immediate off-hook (see end)

- The label in the 'phone is marked as Dial 13. It's not unreasonable to imagine my dad might have changed it (since he was one of those who put the 'unofficial' 'phone system in the student residences at Imperial) but I'm not sure where it would be marked. He did not mention changing it (he died a few years ago, so I'm afraid I can't ask him).

- I am using the original cable to connect the 'phone and the coin box. The colours match the diagram. I'm also using the original (rather sad looking) cloth covered cable between the handset and the telephone - again - colours match the diagram in the phone.

During the testing, as I said above, I disconnected all the wires. Then I looked at the diagram Pellseinydd posted. This interestingly differs from the diagram Dagskarlsen posted - in that 11-13 are linked in Dagskarlsen's, but in Pellseinydd's, only 12 and 13 are linked.

I removed the link from 11-12, wired it according to the diagram, and lo, it worked. I've not compared this wiring to the wiring Dagskarlsen posted - so I'm not sure if there's a significant difference.

Thank you *all* so much for devoting time and effort to this, I'm terribly happy to finally have it working. Now I just need to mount it on the wall and see if I've still got my 'You May Telephone From Here' sign

[dagskarlsen]

Great! It may have been different versions too.
The most important: problem solved, and documented so others may solve it whitout all the struggle.

dsk