What is this component called?

[oldphoney]

Greetings,
First post here, total noob.
Bought a pair of Ericsson BCI 339 telephones, excited to restore them.

One is working well. The second works after comparing the wiring and rectifying a simple inversion — but the sound is a tad crackly and muffled. Not the fault of the earpiece (swapping them changes nothing).

The "good one" has one component that the "bad one" lacks. I know nothing about electronics, and I'm sure most of you will know whether that small block that says "50-A" on the left side is a capacitor, a resistance or a pizza. Would love to buy that component and wire it in.

Thanks in advance for any insights!
Wishing you all a beautiful weekend

[lesmw0sec]

Don't know this phone at all, but the component looks like a fairly hefty inductor. Am I right in thinking that it only has two connections?

Les.

[ThePillenwerfer]

This is little more than a guess but that mystery part may be a buzzer.

As for the poor sound quality, the first thing I'd rule out is the microphone (or 'Transmitter,' to use the correct terminology). Try swapping those as you did with the earpieces ('Receivers').

Good luck

Joe

[keithinuk]

I'm no electrician, but it looks like a 500V 2mf capacitor.
Wrong part

[oldphoney]

Thank you all so much for your replies!

@lesmw0sec Yes, there are two contacts that go straight to the line terminals.

@ThePillenwerfer A buzzer? This phone does buzzes, the other doesn't… Let's open it up and ring the number… Yes! That component buzzes! Terrific, thank you for solving that mystery.

On the "bad one", tried removing then swapping the transmitter as you suggested, but the crackle + distant tone persists.

Attaching a close-up of the buzzer and a shot of the same model in cream.

If I wanted to add a buzzer to the other phone, is that something I need to cannibalize from another old phone, or is that piece easy to buy?

Cheers!

[Nicklyons2]

Try cleaning/spraying contact cleaner into the 'cradle' switch; not unknown for these to give a noisy connexion.

The buzzer is, most likely, not essential and probably included (in the phone which has one) because it was once an extension in, say a bosses office, and the secretary who had the main phone had an instrument with an extra button to 'buzz' the extension. For an idea of how this worked look up British P.O. telephones 'Plan 1A' .

[bobbyball]

Just a quick comment: these phones were not designed to have an internal bell, a typical installation would have a separate wall mounted bell. The buzzer would be fitted where an audible ringing signal was wanted from the phone unit itself. I have converted a number of these (ex-French PTT) phones and there is room inside for a small bell that can be found in plenty on the 'net.

[Station X]

Originally Posted by Nicklyons2

The buzzer is, most likely, not essential and probably included (in the phone which has one) because it was once an extension in, say a bosses office, and the secretary who had the main phone had an instrument with an extra button to 'buzz' the extension. For an idea of how this worked look up British P.O. telephones 'Plan 1A' .

Plan 1A was just a number of phones in parallel. There was no signalling between extensions. I think you're thinking of a Plan 5 or Plan 105.

[oldphoney]

Originally Posted by Nicklyons2

Try cleaning/spraying contact cleaner into the 'cradle' switch; not unknown for these to give a noisy connexion.

Thank you for the suggestion. I tried cleaning between the cradle switch connectors with fine-grit sandpaper and rubbing alcohol, and it helped!

There's still a tiny bit of crackling —don't own any contact cleaner, will look for some. By the way are there other contacts / components that are particularly good to clean?

Originally Posted by bobbyball

I have converted a number of these (ex-French PTT) phones and there is room inside for a small bell that can be found in plenty on the 'net.

Thanks for your historical note. I've looked on EBay and oldphoneworks… Hard to know which bell or buzzer to get. What have you used and liked in your conversions of these ex-PTT phones? For my purposes, not needing the part to be an original.

Now for a juicy detail.
At first I thought that the dials didn't work. Then the Wikipedia segment about pulse rates told me that Sweden and New Zealand were the two exceptions to the standard dial (0 at the bottom, 1 at the top): it went 0 at the bottom, then 1, 2, 3… I tried translating phone numbers (for instance 548-5487 becomes 562-5623), and the dial worked! At the moment my "translator" is pieces of painter's tape (see picture). But I've ordered one rotatone unit in the hope of converting the pulses to tones… Hope it works, we'll see!

[ThePillenwerfer]

Glad to hear that it's progressing.

The dial contacts may well benefit from cleaning as well. I'd advise against using sandpaper on them as they are quite small and relatively delicate. In the absence of contact cleaner, put some alcohol on a bit of card and rub that between them.

I attach a picture of the back of a dial with the contacts circled in red. This is a British one but yours will probably be very similar.

- Joe

[radiotechnician]

As to the unidentified component, it might be an artificial ringer.

The reason might be to make the phone's impedance look like one with a
ringer.

In Canada, in past years, the telephone company could detect the number
of phones on a line by the return kick on a meter, after a voltage was applied.

You might measure the inductor part for resistance and see if it is the same
as another ringer using a 2 uFd capacitor.

[Nicklyons2]

Originally Posted by Station X

Plan 1A was just a number of phones in parallel. There was no signalling between extensions. I think you're thinking of a Plan 5 or Plan 105.

Graham, thanks for that - memory playing tricks again. As an aside though I'm amused to think P.O. Tel could consider connecting phones in parallel officially 'a plan' !

[Station X]

Graham, thanks for that - memory playing tricks again. As an aside though I'm amused to think P.O. Tel could consider connecting phones in parallel officially 'a plan' !

It wasn't so simple as just connecting the phones in parallel. Only one phone had the bell capacitor in circuit and all the bells had to be connected in series. The wiring also had to be arranged to stop bell tinkle on dialling. Each phone apart from one was fitted with a switch to silence the bell by short circuiting it. I believe the version without the switch was a Plan 1B. The wiring of first, intermediate and last phones was different, so all this info was given in an 'N' diagram designated "Plan 1A".

[oldphoney]

@ThePillenwerfer Thank you for the contact cleaning tips and the diagram!

@radiotechnician Thank you — yes, it is a buzzer.

[Pellseinydd]

Now for a juicy detail.
At first I thought that the dials didn't work. Then the Wikipedia segment about pulse rates told me that Sweden and New Zealand were the two exceptions to the standard dial (0 at the bottom, 1 at the top): it went 0 at the bottom, then 1, 2, 3… I tried translating phone numbers (for instance 548-5487 becomes 562-5623), and the dial worked! At the moment my "translator" is pieces of painter's tape (see picture). But I've ordered one rotatone unit in the hope of converting the pulses to tones… Hope it works, we'll see!

If it is a Swedish dial, a Dialgizmo http://www.dialgizmo.com/ not only does the pulse to tone conversion but it will convert the Swedish/NZ pulses to the standard ones. Plus it doesn't involve modifying the line - it is line powered and just sits in the line between the phone and the 'exchange'. And has the 'dial a star' or dial a hash' facility !

Ian

[oldphoney]

If it is a Swedish dial

That's good to know—but that phone has a standard dial.
The power question is a non-issue as the rotatone also feeds on the line (it sits inside the phone).

One possible issue with the Dialgizmo, but not sure: my phone line understands pulse. The rotatone eliminates the pulse so that the phone line only receives the tones, which is what I want, as feeding both pulses and tone on the line would probably not work. It's unclear from the Dialgizmo website if it also suppresses the pulses (they say it's specifically for VOIP lines). If so, that's a good option… and cheaper than rotatone.

[ThePillenwerfer]

The Dialgizmo suppresses the pulses as well.

I've never had to use either but if I did I'd go for the 'gizmo. You need a Rotatone for every 'phone but one Dialgizmo can work with several. At least that's my understanding.

- Joe

[oldphoney]

Thanks guys, the rotatone was ordered a few days ago but for the next phone I might try the dialgizmo.

[dagskarlsen]

Hi
A little late popping in here, NZ and the city of Oslo (Norway) are the only remaining places with reverse dial. Sweden has their own, 1 pulse = 0 2=1 etc.

The buzzer may not be easy to get, but it was used pretty small buzzers in Ericofones (Cobra) in Norway and Sweden. Maybe a miniature ringer for the Western electric prisess, or Automatic Electric Starlite may fit in too.

The noise may as mentioned over be the carbon transmitter, try whats happening with a 220 ohms resistor shunting the transmitter.

Dial pulse rates was commonly 10 pulses pr sec, but the double has been used a few places. Brake make ratios are usually OK even across standards.

dsk