I love watching old movies and TV. Often times they have characters who use telephones via the old switchboard technology. Someone calls into a central system where their call is routed to the proper location.
How did those switch boards work? Especially in comparison to modern phones…
(I would also love any extra info on “party lines” where anyone could join)
In: Technology
Those switching boards connect individual users. Back then when you picked up the phone, someone in the call center answered it. If the line was free, then they would connect you to the other side. What they basically did is connect those 2 endpoints with a cable so you can directly talk to the other.
After that those switching boards where automated. That’s why we have phone numbers, so it can be done without an operator. Rotary telephones used electric pulses to tell the call center who you want to call. Later those rotary dials where changed to the push-button phones. Bell System developed it under the name Touch-Tone, also known as DTMF (Dual-tone Multi-frequency signalling), which is still used today.
Modern phones are much more complicated than the old ones, but the concept is the same. A mobile phone sends out a message to the call center that he wants to talk to this number. The call center then routes that traffic in the direction of the number (to other service providers network for example). If the other side is free then it’s sends back an OK. Audio codecs are selected as well.
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