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Private Telephone System

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Clyd3

New Member
Hi,
I have many, many old telephones wondering around my house, and I was wondering if I could set up my own private telephone line...
The obvious questions being, what power to put on the lines, and where to put it. Please give me as much info as you can, and thankyou....
 

john1

Active Member
Hi Clyd3,

Are these just ornaments?
Or was the place a hotel in a previous life ?

If these are fitted,
then find the 'electrical box' that they all go back to.

If they are just loose telephones decorating the place,
with no fitted wiring, then they need to all run back
to a common box.

There are many circuits for a group of telephones to be
able to ring each other up.

Almost all of them require a main electricity supply.
Almost all of them require a DC supply and lots of chips.

But there are some which run from batteries, and don't use
any current when not in use. I think early Strowger systems
ran from batteries and did not require mains electricity.

If you want to construct a central point (exchange) you
will need to decide whether to construct electro-mechanically
thats relays and similar, or from chips.

To make outside calls on such an exchange, it is usual to
dial a special number first (typically 9 ) to get access to
the normal telephone system. Such small exchanges would
usually have only one incoming line, so a second person
trying to make an outside call from the system would receive
an 'engaged' tone.

I am quite curious about this,
how come you have loads of phones about ?

Regards, John :)
 

Someone Electro

New Member
I have wierles ISDN

There is a base and there can be 8 wierles pohones conected to this base.
Each can call other or more at a time can call in the real thelephone network.

I curently have 2 phones.

its a cool thing! 8)
 

Clyd3

New Member
Where the phones came from?

I dont actually know what there purposes are, most of them have have cables that are chopped off, leading to nothing, one has a cable which leads aimlessly into the roof. I think this must have been an office complex or somthing, and someone decided to scavenge the center of the telephone network. They are all standard phones, just like the one I got with my bought line. Does anyone know how I could make up my own network of phones with internal dialing etc. I've finally got some time to do this, thanks a lot for all the help...(Please suggest a system)
 

Clyd3

New Member
Your wireless isdn

Hey, I'm jealous (but hopefully not for long) I want something like that, someone please help me... PPPLLLLEEEEEEEEEEAAAAAAAAASSSSSSSSSEEEE
 

john1

Active Member
Hi Clyd3,

Yes, you could make up an internal system.
But first, try to see where the phone lines ended up.
I presume they would all go back to the same place,
or most of them anyway.

My guess is an electro-mechanical unit about the size
of a household refrigerator.
Unless its very modern, then it would be chips,
and most likely gone.

If you can find this unit,
you're half way there.

If you find where it was but its gone,
you know where you stand.

In this country, such units were generally in basements.
Although they could of course be anywhere indoors.

You mention the roof space ... could the exchange unit
be in the roof ?
You say their wires are cut short,
but surely you could see where the wires went?
maybe marks in the paintwork?
maybe the old tacks or fixings ?

If you have to make it up from scratch, i would suggest
chips, unless there is a good reason why not.

Even using chips, i think that some electro-mechanical
units would be unavoidable.

If you can find the exchange unit, or even the wreckage
of it, that would be a good start.

Have a look over this page:
http://www.seg.co.uk/telecomm/automat1.htm

Regards, John :)
 

Clyd3

New Member
There seems to bea little marking in the roof, showing a box about a meter tall, and half a meter wide... Nothing left... I think I'll do some searching around to try find some setup, maybe if I could find info on how the telephone networks found in offices work, then i could make my own.
 

john1

Active Member
Hi Clyd3,

I'm very sorry to read that the exchange unit has nothing left.
I take it you are fairly sure that was the place where the phone
wires went, it sounds about the sort of size i would expect,
about the size of a household fridge.

That leaves you with a lot of learning and a lot of work if you
want to link together twenty or more telephones.
( how many do you intend to join up ? )

Did you look over that link i posted for you ?
http://www.seg.co.uk/telecomm/automat1.htm

Theres plenty of stuff on the net about this sort of thing,
i'll see if i can find you some diagrams to look over.

Regards, John :)
 

john1

Active Member
Hi Clyd3,

If you go with an electro-mechanical set-up,
this is the sort of thing you would be looking at:
http://www.seg.co.uk/telecomm/automat4.htm

I think that making it out of chips would probably be cheaper,
unless you can get relays and selectors easily or cheaply.

John :)
 

Dialtone

New Member
What you ask for is not so easy as it may sound. I have spent over 30 years in the telephone industry and have seen all manner of switches from electro-mechanical (Step-by-step, crossbar) to analog computer controlled, to all digital. But I can give you some of the basic information for an electro-mechanical system.
1. Line voltage to the phone is typically -48Volts DC (talk voltage). You can get by with less than this on a direct phone to phone connection if the length is short. I have seen some diagrams for a direct circuit usng a transistor radio 9 volt battery, but think it would drain fast in use.
2. Ringing voltage is typically between 86 to 105 volts ac at 20 cycles per second. The ringing is tripped (removed from the line) by detecting DC current flow in the line when phone is picked up, cutting off the ringing supply to the line.
3. Dial phones are typically set to give a 10 pulses per second make/break rate during dial return. This was used to step the switches in the electro-mechanical systems. Each digit dialed would step a switch segment to the dialed level and cut thru to the next switch segment for the following digit.
4. Push button phones use a dual tone signal in place of the pulsing of the dial (called DTMF) (be advised, there are 2 kinds of DTMF used in telephone systems. 1 for phone to switching center, and another for signaling between offices. Each uses different frequencies of tone to represent the digits) There are chips available to encode and decode dial DTMF available at most electronics stores if you want to experiment a bit.
How is that for a start?
Dialtone
 

Clyd3

New Member
Hey, thanks for the info, Dialtone. Just a few questins this time: Is the voltage +48V or -48V? (just to be sure before I start). Secondly, in the phone tapping, we only seem to tap 2 lines out of the four, in fact, my phones only use two, (I think), why is there four, what are the other two for?
 

Dialtone

New Member
Line voltage is negative 48 volts DC. This means that the positive side of the line is the earth ground refrence point. Only 2 leads are used in the talk path. Most phone cords have 4 leads in them and standard wall jacks have provisions for 4 conductors also. In some cases, you can get a 2 line phone that uses the other wire pair for the second line. Some older phones with illuminated dials used the second pair to supply low voltage AC to light the dials from a wall transformer. They can be used for just about anything you need them for, but mostly they are a confusion factor.
Dialtone
 
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