Looking for a vintage intercom set

[BigClick]

Originally Posted by AC/HL

If you don't mind both phones ringing on an incoming call, wiring them in parallel and unmodified for plug and socket working should get bell tinkle when loop dialling. Dial 9 and you will be able to speak phone to phone until the howler cuts in. Should suffice for a stop gap.

We used to use things called "Barretas" to stop bell tinkle

[boombox]

Originally Posted by BigClick

Bellset 20 would be ideal
I just happen to have one that I could let go at forum buddies rate

Thanks - very interested - shall I PM you?

[TonyDuell]

Originally Posted by AC/HL

If you don't mind both phones ringing on an incoming call, wiring them in parallel and unmodified for plug and socket working should get bell tinkle when loop dialling. Dial 9 and you will be able to speak phone to phone until the howler cuts in. Should suffice for a stop gap.

A kludge which a friend and I rigged up when I stayed at his house some 35 years ago :

A pair of 700-series telephones, wired for a normal 2 wire line. Connect them in parallel. Now power them by connected a current-limited PSU of about 30V across the parallel-connected telephones. The PSU must be able to stand a short-circuit and have a fairly high impedance. I think we used a 24V PSU and a couple of car bulbs in series as the limiter.

The idea is that if you lift the handset of one telephone and dial zero, the bell of the other telephone will tinkle. Pick up that one and you will get speech transmitted between them.

An inductor in series with the PSU helps, both to add some more impedence at audio frequencies and to give a higher voltage when the dial contacts break to tinkle the bell. But too high an inductance and the dial impulse contacts suffer.

[OscarFoxtrot]

If you want to build one:

http://www.classicrotaryphones.com/f...p?topic=6141.0

[Nickthedentist]

Originally Posted by BigClick

We used to use things called "Barretas" to stop bell tinkle

Usually spelled "barretter".

In contrast, a "Beretta" is a type of gun.

Don't get your blowers and shooters mixed up!

[TonyDuell]

The other thing that occured to me is that if you look at amateur electrical books of about 100 years ago there were several designs for build-your-own intercom telephones.

I am not suggesting you have to make the carbon microphone, earpiece, induction coil, DC bell/buzzer etc. Rather that you could take parts from damaged 700 series telephones and build something similar.

[OscarFoxtrot]

Another option is the stanophone circuit.

Used a two-coil DC buzzer/relay to generate a nasty buzzing sound in the earpiece.

http://picclick.co.uk/ITT-STANOPHONE...l#&gid=1&pid=4

[Pellseinydd]

Originally Posted by Nickthedentist

Usually spelled "barretter".

In contrast, a "Beretta" is a type of gun.

Don't get your blowers and shooters mixed up!

Barretas can be used to provide 'bell tinkle' if you get the aim right

The GPO used baretters in transmission circuits for limiting line current.

Thermistors were used to prevent bell tinkle - i.e. 'Thermistor 1AN' in the Tele 314 http://www.samhallas.co.uk/repositor.../0000/N414.pdf or the little tag ended 'Thermistor 1A-1' which was added to convert a Tele 706 for shared service auto working as per diagram N806 Figure 2 http://www.samhallas.co.uk/repositor.../0000/N806.pdf

Ian

[Herald1360]

Originally Posted by Nickthedentist

Usually spelled "barretter".

In contrast, a "Beretta" is a type of gun.

Don't get your blowers and shooters mixed up!

And don't mix either up with a biretta or you might get into all sorts of trouble

[Ed_Dinning]

Hi, I believe there was a Wireless World "home telephone exchange" design in that magazine in the 70's.

This could take up to 2 incoming lines and supply upto 10 extensions with calling between extensions as well.

Ed

[julie_m]

For less than the cost of the parts for that, you could pick up a Digium TDM410P clone which, with the free Asterisk software, will turn a scrap PC into a full-blown telephone exchange. Cards are available from The Usual Places and can be configured with any combination of up to four FXS or FXO modules.. You need an FXS interface to connect to a phone, or FXO to connect to an exchange line. Probably best to get 3*FXS and 1*FXO. Supports pulse dialling, so ideal for use with vintage phones. Can also be configured to dial a number as soon as a handset is lifted, for use with dial-less phones.

[PsychMan]

Originally Posted by boombox

That looks brilliant, but I guess I'd have to find a VoIP adaptor suitable for use with BT plugs?

I've done this myself, you can modify it quite simply to work over IP between 2 VOIP devices (1 per phone), in which case you can use Ethernet cabling or even wifi with wifi routers added. Myself I'd run some cat6

[Voxophone]

Originally Posted by Ed_Dinning

Hi, I believe there was a Wireless World "home telephone exchange" design in that magazine in the 70's.
This could take up to 2 incoming lines and supply upto 10 extensions with calling between extensions as well.

That sounds like an interesting project.

[Voxophone]

It's mentioned here, but the article is for another system: http://www.aholme.co.uk/Exchange/Design.htm

Edit - Here is a PDF of the original: http://www.classicrotaryphones.com/f...p?topic=6218.0

[BigClick]

Originally Posted by Pellseinydd

Try eBay - this firm has had them in stock and I and others on CNet (The replica of the old GPO phone network using VoIP) have used them for years

I dont dispute you had good service but I have tried twice and lost one lot of cash

[BigClick]

Originally Posted by Nickthedentist

Usually spelled "barretter".

In contrast, a "Beretta" is a type of gun.

Don't get your blowers and shooters mixed up!

oops

[Pellseinydd]

Originally Posted by BigClick

I dont dispute you had good service but I have tried twice and lost one lot of cash

And yet they have 100% feedback!

[BigClick]

Originally Posted by Pellseinydd

And yet they have 100% feedback!

So I ordered one and it never showed. When I contacted them they apologised and said they would send it again.

I had forgotten about it until this thread started up. Too late for feedback now on "my Ebay"

No disrespect meant Ian.

[Station X]

Please let's not have any further discussion about the merits or otherwise of eBay sellers.

[Ian - G4JQT]

Maybe more effort that you'd like, but I made some intercom telephones at school in the early 70s which I still have and use!

They are from a design published in The Boy Electrician. There are two designs, one using transformers for better audio, but I made the simple version, the circuit is shown on page 191 of the edition of the download below. (There are various republications/reprints.)

You can simplify the design by using ordinary battery bells and telephone handsets, mic and earpiece modified to be wired in series - just check the current pulls the diaphragm in not out.

Then at each unit and a 4.5 or 6 volt battery.

I made the cases in woodwork and used some stiff sheet cut to hold the handset and operate the hook switch.

There's an official free download of the book here:

http://rawfire.torche.com/~opcom/tbe...lectrician.pdf

Mine work over about 100 yards easily.

Certainly vintage if you make them exactly to the 1930s original design!