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.
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 > >> 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 1928...by
> 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.