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Old 26th Jul 2019, 10:54 pm   #1
ManxDave
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Default Vintage Arrow ( Toy? ) Telephones

I am more into old radios than telephones but these were given to me to see if they can be made to work. Can anybody tell me what is needed to be done?
As far as I can see, electrically each telephone only has an ear and mouthpiece, a relay and a switch for when the handset is lifted.
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Old 27th Jul 2019, 1:48 am   #2
Mr Moose
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Default Re: Vintage Arrow ( Toy? ) Telephones

Hello,
This is pure guesswork but I think what you call a relay may be a buzzer.
If you look carefully there are two thick metal prongs that stick out in each phone and where they meet the plastic case there appears to be a + and - sign cast into the plastic so presumably a battery or batteries fit in there possibly held in place by the piece of thick wire that goes across.
If this is correct you might have to use trial and error to determine the correct battery voltage.
Yours, Richard

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Old 27th Jul 2019, 4:27 am   #3
TonyDuell
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Default Re: Vintage Arrow ( Toy? ) Telephones

There were many similar units, sold as toy intercoms (e.g. between a child's bedroom and their parents). Most of them (but it appears not yours) had some kind of calling switch that you operated to sound the buzzer in the other telephone. In one of my sets it's a contact operated when the imitation dial is off-normal.

But anyway. The most likely candidate for the battery is one of those flat 4.5V units with the brass strips on top. I knew it as an 1289. Is that a 3LR12 now? Try one in each telephone.
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Old 27th Jul 2019, 9:21 am   #4
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Default Re: Vintage Arrow ( Toy? ) Telephones

Possibly simply lifting the handset on the calling phone activates the buzzer in the called one. Lifting the called one completes the speech loop and silences its buzzer.

The speech circuit is probably a simple series connection of all microphones earpieces and batteries. Should be easy enough to reverse engineer if enthusiastic.
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Old 27th Jul 2019, 9:37 am   #5
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Default Re: Vintage Arrow ( Toy? ) Telephones

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Originally Posted by Herald1360 View Post
Possibly simply lifting the handset on the calling phone activates the buzzer in the called one. Lifting the called one completes the speech loop and silences its buzzer.
The problem with that is that you need the microphone/earpiece in series with the loop at the calling telephone when you are speaking but they have rather too high a DC resistance to be in-circuit when sounding the buzzer. I seem to remember that in some (most?) of these telephones the calling switch just shorts out the microphone/earpiece and puts the battery to the interconnecting cable.


Quote:
Originally Posted by Herald1360 View Post
The speech circuit is probably a simple series connection of all microphones earpieces and batteries. Should be easy enough to reverse engineer if enthusiastic.
All the ones I've seen have a 2-wire handset cable and the microphone/earpiece are in series in the handset.

Normally the 2 telephones in the set are indentical, but the line wire is cross-connected (so the left-hand socket contact on one telephone goes to the right hand one on the other, for example). These means the batteries end up in series adding their voltages.

I must dig out one of my sets and reverse-engineer it. It won't take too long...
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Old 27th Jul 2019, 9:39 am   #6
ManxDave
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Default Re: Vintage Arrow ( Toy? ) Telephones

Thanks for the three replies. I will mend the broken connections with all the mouth and earpieces in series and see what happens with the batteries suggested.
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Old 27th Jul 2019, 9:41 am   #7
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Default Re: Vintage Arrow ( Toy? ) Telephones

Thanks for the update Tony. If you get chance I'll wait for your confirmation.
Dave
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Old 27th Jul 2019, 7:28 pm   #8
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Default Re: Vintage Arrow ( Toy? ) Telephones

I just had a play with a notepad and pencil drawing up some sketches, and I think it can only work as follows:
  • When the handset is on the rest, the buzzer is connected across the line to the other phone.
  • When the handset is lifted, the battery, microphone and earphone in series are connected across the line to the other phone. Current flows from your battery, through your microphone and earphone, and their buzzer. The trembler contacts are interrupting the current through your earphone, so you hear a sound of the same frequency.
  • When the other person picks up their handset, the buzzer is disconnected and.their battery, microphone and earphone are placed in series with yours.
Note that if the batteries are wired the same way around in each unit, the line wires must be crossed over; if the batteries are wired the same way around and the line wires are connected like-to-like, the batteries' voltages will cancel out rather than adding together. This will result in buzzer action, but no speech.

The first thing to do probably is to use an ohmmeter to check for continuity through the handsets, buzzers and switch contacts. (The buzzer is actually a relay, although it's wired in an unusual way: it has a normally-closed contact in series with its coil and when energised, it switches itself on and off repeatedly at a frequency which you hope is within the sensitive range of human hearing. You should see the resistance reading go from a few tens of ohms to overload, if you operate the contact by hand.)

The fidelity of these units is not great, and anything less than perfect connections throughout will make it worse; but they were a nice novelty back in the days when we were all more easily amused .....
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Old 27th Jul 2019, 9:38 pm   #9
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Default Re: Vintage Arrow ( Toy? ) Telephones

A typical circuit may be like this.

PS forgot the call button. The button just shorts the handset.

DS
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Old 28th Jul 2019, 3:23 am   #10
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Default Re: Vintage Arrow ( Toy? ) Telephones

I did actually think of another way they could be wired. This would be a sound-powered arrangement, with the batteries used only for calling. It would need the microphones to be dynamic types (probably identical to the earphones) rather than carbon types. Wiring them in parallel rather than series would allow more current from the battery to the buzzer. (Either way, at most only one-third of the energy from the microphone actually makes it to the other party's receiver; one-third goes into your ear, and the remainder is wasted in the other party's mic. And that's not accounting for what gets swallowed up in line losses ..... Of course, you are speaking at full volume straight into the microphone, while they have their ear pressed tightly against the receiver; so as long as the total electrical losses are still less the inverse square law losses of sound travelling a few metres across a room, things are still pretty much in your favour.)
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The left hand phone is shown with the handset on the rest. The right hand phone is shown with the handset lifted. Current flows from the called party's battery, through the calling party's handset and the called party's buzzer. When both handsets are down, the batteries are wired so they fight against one another; the voltages are equal, so no current flows. When both handsets are up, the batteries are out of circuit altogether and the only energy sources are the microphones.

At any rate, it should not be too difficult to sort out the wiring scheme inside each phone unit if you have them there in front of you.
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Old 28th Jul 2019, 8:17 am   #11
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Default Re: Vintage Arrow ( Toy? ) Telephones

Quote:
Originally Posted by julie_m View Post
When both handsets are down, the batteries are wired so they fight against one another; the voltages are equal, so no current flows.
This is presumably only strictly true if the two batteries have equal charge. Is there a possibility that a discharged battery could result in enough current from the other battery to operate the buzzers? This could either be seen as a b***** nuisance or as a "battery low" indicator (or both, like those smoke detectors that go bleep in the night).
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Old 28th Jul 2019, 9:14 am   #12
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Default Re: Vintage Arrow ( Toy? ) Telephones

Batteries in series opposing would have to be in very different states of charge for the buzzers to sound. Only the difference between the two voltages is available to push a current, and the resistance is the two buzzers in series. The resulting current is unlikely to be enough to pull in either of the armatures enough to break the circuit, so the buzzers will stay silent until eventually the states of charge have equalised.

It's not even certain this configuration is actually used (but it would be a good way to minimise the voltage drop across the handset during calling).
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Old 28th Jul 2019, 10:35 am   #13
ManxDave
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Default Re: Vintage Arrow ( Toy? ) Telephones

Thank you all. A wet Sunday morning on the Isle of Man is an ideal time to connect this up and make some resistance readings whilst waiting for the batteries. I'll let you know how I get on and yes Julie simple things still provide me with more amusement than modern technology.
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Old 28th Jul 2019, 2:16 pm   #14
TonyDuell
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Default Re: Vintage Arrow ( Toy? ) Telephones

As promised here are some reverse-engineered circuits of similar telephones in my collection. They're all similar (and similar to the circuit Julie posted). It's quite an old design, I've found much the same circuit in books over 100 years old.

All mine have some kind of calling button to connect the battery directly to the line to sound the buzzer/bell at the other end.

One thing I'd not thought of was putting the transmitter (microphone) and receiver (earpiece) in parallel (one of mine is wired like that). It will work and it might be possible to have components with a low enough resistance to be able to sound the buzzer with the handest in-circuit, as suggested in an earlier post.
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Old 28th Jul 2019, 9:19 pm   #15
ManxDave
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Default Re: Vintage Arrow ( Toy? ) Telephones

Thank you all, I have it working. I think with the circuit below. I haven't checked whether the earpiece and mouthpiece are in series or parallel.
Despite it being very basic it took quite some time to sort out a collection of minor faults. The handset/gravity switch was mechanically sticky on one, on both it was high resistance on the buzzer side ( back emf from the coil ? ). One buzzer contact was open circuit ( or very high resistance ) when it should have been closed and the brass spring loaded connectors were very tarnished, cleaning them lowered the resistance there.
Voice quality is pretty poor but it is only a toy and it may improve when I get the correct batteries fitted.
Thanks again Dave
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Old 31st Jul 2019, 7:00 pm   #16
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Default Re: Vintage Arrow ( Toy? ) Telephones

Great, you have the right battery voltage when you have enough to get more than 25mA trough the handsets, and less than 60 mA (more wil fry the transmitters (microphones))

Ususally 3V on each should do, but more on long lines to get enough to activate the ringers.
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Old 31st Jul 2019, 7:14 pm   #17
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Default Re: Vintage Arrow ( Toy? ) Telephones

Thanks. The telephones looked styled to fit the 4.5V 1289 / 3LR12 batteries Tony mentioned above but I will double check the handset current when the batteries arrive.
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Old 31st Jul 2019, 9:37 pm   #18
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Default Re: Vintage Arrow ( Toy? ) Telephones

If that they are made for 4.5V batteries that might be right. If the current has been to big, it may be a reason for the sound-quality. If you replace the carbon transmitters with electronic replacement capsules the voltage mau be adjusted to work well, but you will not know bwfore you have tested...

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