TELECOM Digest Editor noted in response to Neal McLain :
When automation finally started, in 1938, Illinois Bell started
> printing all numbers (dialable or still manual) in the telephone
> directory as names plus FOUR digits, using leading zeros as required
> to complete the string. ... from 1938 until 1946 Chicago was about
> 20-50 percent dial and the same amount manual. PAT]
Just wanted to a note another reason why they did this: The Bell System plan for large cities was the "panel system". They knew it would not be converted to dial overnight. Also, cities and suburbs were growing and modest manual exchanges could soon grow into big exchanges. (In the 1920s the cities were developing new dense neighborhoods rapidly). The panel system was designed to provide for all of this.
The panel system was 'common control' in that it had some intelligence designed into it. Unlike step-by-step where each dial pull controlled the direct switch, panel stored the number in a register, translated it to proper routing, and made a connection from the translation. This gave the necessary flexibility for city networks.
Panel also provided automatic assist for dial-manual interconnections. The idea was that dial customers would not need to know the type of exchange they were calling, they would dial the 7 digit number in all cases. If they were calling a manual office, the system would route the call to the exchange, and convert the last 4 digits to a readout on the operator's switchboard. The manual operator would make the connection based on the readout. For calls from a manual exchange, the operator would merely dial the desired number. (I'm simplifying this quite a bit).
As an aside, for some reason I don't understand, panel could NOT be used for Centrex service, though the older step-by-step could (along with crossbar and ESS). In SxS, they merely wired the terminating selectors to serve as the Centrex switch, very simple. I don't know why panel's logic circuits couldn't handle it.
In the literature, it says a manual exchange could have 10,500 numbers and an extra digit was provided for that. How often that was used in reality I don't know; perhaps just in NYC with its very high density calling.
Panel also provided meters to count up local calls to charge message- rate service.
I believe (need to confirm) the meters were also used to time calls in NYC, that is, after say five minutes, the meter incremented again. As to suburban calls, the meters would work out fine for message units, but calls still may have been internally processed with full AMA details even if the customer only saw a meter count, not itemization.
(To this day, city suburban calls are charged by message units or "measured service", in which units are changed based on distance and time. The customer doesn't see itemization of a bunch of 15c and 25c calls, rather just an accumulation. In Phila, the Verizon reduced the charges, widened the free area, and gives off peak discounts. However, the basic system remains in place to this day unless you buy a wide area calling package. Consult the front of the Verizon Philadelphia phone directory for details.)
(For myself, national unlimited was only a few dollars more than local wide area, so I now have national unlimited. For someone who remembers when making a long distance call was serious business, free calling is a bit strange and takes some getting used to.)
[TELECOM Digest Editor's Note: The single, isolated example I ever saw of a manual phone with FIVE digits after the exchange name was in Hammond, Indiana when I was about 11-12 years old. A payphone in the parking lot of a grocery store carried the number 'Sheffield 10523'. Note that was NOT 'Sheffield-1' but rather, a manual exchange 'Sheffield' followed by '10523' as the number within the exchange. Hammond, the first of the Indiana cluster of Chicago southeast suburban suburbs to 'go dial' about 1953-54 converted their Sheffield exchange to WEstmore 1 and WEstmore 2; and their Russell exchange to WEstmore 3 and TIlden 4. And in those days, WEstmore and TIlden anything could seven digit dial Illinois-side south suburbs, and vice- versa, but Chicago itself required the leading 219 to call Indiana. For many years, there was no 312-931, 312-932, or 312-933 since those would have conflicted with Hammond's exchanges. Bell finally cut in
312-659 (Whiting, IN has 219-659) in 1982 and gave it to Cellular One for cell phones. Now it is no longer '312'; I suppose now it is 773 or maybe 630. PAT]