Self-Contained Rotary Dial and Electro-Mechanical Telephone Exchange Demonstrator.
Purpose:
To entertain and educate my grand kids.
What It Does:
It is a basic 3 digit telephone exchange that demonstrates, in a small way, how telephone calls were completed using rotary-dial telephones and electro-mechanical switching equipment that were in use from 1890's until the 1990's.
It allows the younger generation to learn how to dial a rotary dial telephone and appreciate the way telephone calls were completed before smart-phones.
Background:
My 35 year career with the phone company (GTE then Verizon), began in a step-by-step Central Office, filled with tens of thousands of Strowger Selectors and Connectors like seen above.(Also; Line-Finders, Directors, Translators, Ticketers, Register-Resenders etc. but that's another story).
Challenges:
To provide the following items that were normally supplied by the Central Office:
What Was Done:
To entertain and educate my grand kids.
What It Does:
It is a basic 3 digit telephone exchange that demonstrates, in a small way, how telephone calls were completed using rotary-dial telephones and electro-mechanical switching equipment that were in use from 1890's until the 1990's.
It allows the younger generation to learn how to dial a rotary dial telephone and appreciate the way telephone calls were completed before smart-phones.
Background:
My 35 year career with the phone company (GTE then Verizon), began in a step-by-step Central Office, filled with tens of thousands of Strowger Selectors and Connectors like seen above.(Also; Line-Finders, Directors, Translators, Ticketers, Register-Resenders etc. but that's another story).
Challenges:
To provide the following items that were normally supplied by the Central Office:
- 50vdc power for the Strowger Switches.
- 25 cycle ringing generator to ring the called telephone.
- Office tones. (Dial tone, ring-back tone & busy tone)
- Disconnected number announcement.
- "Celebrity" numbers to call.
What Was Done:
- To power the Strowger Step-By-Step switches, I constructed a 50vdc power supply using a step-down transformer and a “pi” section filter of 2 capacitors and a resistor.
- For the ringing generator, I built a 25 cycle power supply using a 555 timer chip and a door bell transformer used as a step up transformer.
- For the office tones, I used three record/playback modules for the dial, ring-back & busy tones. All are recorded with actual rotary-dial era Central Office tones for added realism.
- Another record/playback module is used for the disconnected number recording..
- The "Called Telephone" is provided with a 3 digit phone number, for answering calls.
- Just for fun, I added more record/playback modules with the voices of Mickey Mouse, Darth Vader & Scooby Doo answering the telephone. Each with its own 3 digit phone number which automatically answers when dialed.
- Unassigned phone numbers either go to Busy Tone or Disconnect Recording
- One 3 digit phone number allows a caller to record their own message and then dial another number to play it back.
- The "payphone motif" on the called telephone is just for whimsy.
