History of 1+ Dialingby Colin Berkshire in Telecom
If you grew up on the east coast in a large city you probably think 1+ dialing is weird, or an inconvenience. You never dialed 1 before a “long distance” call. You just dialed the 7 or 10 digit number. What could be simpler?
If you grew up on the west coast, or a smaller city you had the comfort of knowing that the digit 1 was required before an expensive “long distance” call. If you didn’t need to dial a 1 then the call was a local call. It was a nice form of protection from surprises on your bill.
But this isn’t at all why 1+ dialing existed!
The necessity of dialing 1 before toll-calls was because step-by-step switching systems had no memory and actually had no awareness of the entire phone number you were calling. Each piece of machinery would accept one single digit and then pass you to the next piece of machinery. So after a dial tone dialing digit 4 would send you to all of the switches wired under control of the first 4 machine. This second machine would take the next digit, perhaps 5. And so on. So every digit needed a separate machine and they were all physically wired together with each machine being accessed by a previous one. But the machine was an idiot, and it didn’t know what number you were calling from or what number you were calling to.
Larger cities used Panel central offices, and in later years they used Crossbar. These were relay based systems, but they had memories. There were “registers” which were a bank of relays and a wired-logic computer. Four relays could store a digit. So with just 40 relays you could store an entire 10 digit number.
These registered were smart and complicated. They could know if a number was long distance. They could know if you had metered service. They knew your phone number. Because of this, they could do billing. They could note your calling number, the number you dialed, and the start-time of the call. They had everything necessary to make long distance calls. There was no need for a “1” in front of the number.
But the poor, stupid step-by-step switches were idiots. So when you dialed “1” the switch sent you immediately off to a different switching system that could collect your digits (to see what number you were calling) and to do the billing.
The need for a digit 1 was simply so that if you happened to be in a step-by-step switch you could get out of it.
Since some operating companies tended to have predominantly step-by-step switches those areas were 1+ areas. Mostly, this was the west coast and small cities, where step-by-step was most economical.
More densely populated areas had Panel or Crossbar switches and no need for 1+.
But the Bell System decided to advertise 1+ dialing nationwide since that would work wherever you were traveling to. When a Crossbar or Panel office saw the first digit was a 1 they would ignore it, but turn the dial tone off. Nothing more.
1+ dialing came about solely because of the prevalence of step-by-step switches.
So if you grew up dialing 1+ for long distance calls, you came from an area that in the 1950s and 1960 had a lot of step-by-step switching. If you grew up not dialing 1 before a long distance number you came from a big city, where there were Panel and Crossbar offices.