Comments on: How To Fix Old Telephone

By: Albert van Bemmelen

Albert van Bemmelen — Thu, 19 Oct 2017 12:40:37 +0000

I tried to email following link to you Humberto but sending it failed somehow. I made 28MB of quality photos about the mentioned DTF dialer that probably fits in your old phone too:

https://mega.nz/#!wwZgQTpS!Rxpew--piK_PqaCGveMKIH8gWJT_CnHR4qQYRQP6SyU

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By: Henrique Jorge Guimarães Ulbrich

Henrique Jorge Guimarães Ulbrich — Wed, 18 Oct 2017 21:53:16 +0000

Humberto, for me this telephone set is even older than 50 years. Perhaps it was produced before 1950!

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By: suranag Electronics

suranag Electronics — Sat, 14 Oct 2017 08:35:26 +0000

hi. Mr.Humberto,

Wow.. very nice Old Phone Repair.
i have no Any Experience old phones Repairs.

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By: Albert van Bemmelen

Albert van Bemmelen — Fri, 13 Oct 2017 20:31:24 +0000

In reply to Albert van Bemmelen.

About that old DTF number dialing unit I was telling about: I have one here and I made photos of the dialer if someone is interested.
It indeed is connected to the Phone through 4 wires internally. And it does have two transformers with each 2 x 5 connection pins. And every time a number is pressed a contact with 3 connections is switch open and also closes another one. And the round front 0-9 number dialing keyboard is attached with 10 wires to this board.
The board also does contain two transistors, a diode bridge (BY159 400V) , 8 diodes, 2 capacitors (1 x 33nF and 1 x 68nF 200V), a couple of resistors and a probably 2 special ntc or ptc resistors for temperature/ frequency stability. So likely a unique DTF tone is produced when any coil in each of the 10 coils in both transformers is active coresponding with the key that is pressed.
Knowing this construction was made in a time before chips or microprocessors were standard components, this also means that todays DTF method already was 'invented' in that time.

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By: Yogesh Panchal

Yogesh Panchal — Fri, 13 Oct 2017 17:14:30 +0000

Humberto,

Good to see the old Dial type telephone back to the life .

we also have used this type of phone for almost 40 Years but we have to replaced it because it does not support tone dialing.

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By: Robert Calk

Robert Calk — Fri, 13 Oct 2017 12:53:36 +0000

Good job, Humberto. Hopefully we will start seeing some good USA made products again soon.

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By: Anwar Shiekh

Anwar Shiekh — Fri, 13 Oct 2017 12:20:32 +0000

Found this:

Federal Telephone & Telegraph Co. originally was named Century Telephone Construction Co. Century Telephone was founded in Cleveland, OH in 1899. They moved to Buffalo, N.Y. in 1902. sometime after 1907 Century changed it's name to Federal Telephone & Telegraph and operated under that name until 1920's when the name was again changed to Federal Telephone & Radio Corp. in 1956 the company was purchased by International Telephone & Telegraph (ITT)

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By: George Greenfield

George Greenfield — Fri, 13 Oct 2017 12:14:00 +0000

Yeah...
they don't make em like they used too do tey?
I have several old rotatory phones.
They still work. I like to show them to young folks what phones looked like in the old days.

Great job. Keep em running as long as we can !
George

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By: Parasuraman

Parasuraman — Fri, 13 Oct 2017 08:39:05 +0000

Vow! Happy to see this model still working! A nostalgic instrument! A good job there, Humberto.

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By: Albert van Bemmelen

Albert van Bemmelen — Fri, 13 Oct 2017 06:17:02 +0000

Nice article with always appreciated schematic Humberto. These old (bakelite?) telephones still with old carbon microphone and earphone, with rotary turntable/dial selector are not made for todays modern digital telephone exchange/call centres which are made for tone dialing (DTF-dual tone frequency) instead of Pulse dialing. And are unable to use when you need to press a number of a menu when you phone your doctor or any official phonenumber that require us to select from given options. I however know that you can take out your old rotary dialing part and replace it with an old but perfectly DTF number dialing selector. It produces those modern DTF tones with just coils and other electronic parts without any microprocessor and maybe not even any semiconductor in its part. Just screw the 4 wires (i think they are 4?) wires of that DTF dialing unit in place of the old rotary dialer and you have a upgraded modern device.

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