Telephones with dials

You used to have to know someone’s telephone number to be able to dial it. It wasn’t a matter of pressing a name in the contact list in your smart phone and relying on technology to do the rest. Oh, no.

You picked up the telephone receiver — possibly perched on your telephone table — and waited until you heard a dial tone. Then you placed your finger in the hole of the first number you wanted to dial, and twirled the dial clockwise until your finger reached a small curved bar. At this point, you removed your finger from the dial and let it spin all the way back to its resting position. As it went spinning back, the dial mechanism wound a spring and sent a set of pulses down the line.

You then put your finger in the hole in the dial for the next digit of the phone number you were trying to reach and repeated the process. And repeated the process again until you’d entered all the digits. The pulses routed the call to the number dialled. With luck, you might have entered all the digits correctly and the right telephone far, far away would start to ring.

If no-one answered or the line was busy, you’d have to manually dial the whole sequence again. Automatic redialling was a dream. Features such as Caller Display or Call Waiting were a distant dream.

black_telephone

Now more frequently seen in antique shops than on telephone tables

For all its apparent clunkiness today, the dial was a practical and elegant mechanism. Yes, you had to wait while the dial returned to the start, which was tedious, but it also meant the system had built-in resilience. An electro-mechanical switching system needs time to recognise a string of pulses as a specific number. If there is a pause between one set of pulses and the next, the system knows you meant to dial 4, 3, say, rather than 7. The dial-return mechanism provided a convenient pause; you had to wait until one set of pulses was sent before you could send the next.

Pulse dialling gradually gave way to tone dialling — where each digit corresponds to a specific tone — which connects calls almost instantaneously. Out went the dial. In came the buttons. We may still dial a number… but very few of us do it using a dial. If you want to, though, you could. Many exchanges still support pulse dialling.

You’d be at a bit of a loss, though, when it came to pressing 1 in an attempt to speak to a human.

rotary_dials

 

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