TELECOM Digest OnLine - Sorted: Re: Old Chicago Numbering

Re: Old Chicago Numbering

Tony P. (
Mon, 31 Oct 2005 18:43:17 -0500

In article <>,

> Ma Bell (sorry, old habit) had 'standard builds' for large metro
> offices and seemed to follow them quite consistently over the years.
> Their upgrades seemed to follow these patterns:

> Panel -> 5Xb
> Panel -> ESS
> 1Xb -> ESS
> 5Xb -> ESS

> and, of course,

> SxS -> ESS (mostly CDO, PBX, etc.)

> We won't even talk about the 101ESS. <big snotty grin>

Providence, RI went from Panel to ESS. It had to have been around 1972
or so since we'd moved from a location in the city that only had
rotary dial service to one that had DTMF and the definite ESS call
progress tones.

I do recall that they really stretched out the cutovers. My
grandparents house in Providence still had the old style call progress
tones indicating they were still on the Panel until 1975 or so. The CO
for most of Providence is a huge building -- at least 14 floors that
were once filled with switching gear. Now it's just the 4th floor. The
rest of the building is offices.

I do recall moving from Providence, RI to North Providence, RI and
being stuck on the #5 Xbar serving Pawtucket. It was a fun machine
what with its loopbacks, etc. When they cut to the #5 ESS it was like
losing an old friend.

In article <>, says:

> In a message dated Sun, 30 Oct 2005 14:21:21 CST,
> writes:

>> Very seldom did Ma Bell use SxS for large metropolitan installations.
>> They seemed to prefer remaining with manual service until they could
>> install 'machine switching' using Panel or later 1Xb.

> "Very seldom"? How about Dallas, Houston, San Antonio, Tulsa,
> Oklahoma City and, of course, much of the Los Angeles area.
> Undoubtedly true of many other places as well..

> All those had been completely converted to dial by the early 1930s,
> perhaps in the 1920s. The first dial office in Oklahoma City was cut
> over in early 1921 (using Automatic Electric SxS equipment; Bell Labs
> and W.E. had not yet recognized there was a need for such equipment.
> The remainder of the city was converted to dial in 1927 or
> this time with W.E. SxS equipmenmt. I think the remainder of the
> cities mentioned in Texas and Oklahoma had a similar history.

> The first XBs in Southwestern Bell territory outside of Kansas City
> and St. Louis were 5XBs in smaller towns converting to dial. The
> first 5XB in Oklahoma City was the SKyline office, now 751, which
> happens to still serve where I live (now ESS of course).

> One of the first installations of 5XB in the Los Angeles area was by
> the Sunland-Tujunga Telephone Company.

> 1XB, of course, was intended to be use in metropolitan areas that were
> panel. As originally configured it used on panel-type revertive
> pulsing -- even when one 1XB office was communication with another 1XB
> office. It had no provision for communicating with step equipment,
> which is why the 1XB installations in Southwestern Bell territory were
> limited to St. Louis and Kansas City.

Even the 5XB understood revertive pulsing. Some of them ended up as
minor toll tandems for the remaining Panel switches in an area.

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