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Historical 4A 4M Crossbar Tandem List - Telephone World The following is a historical listing of the former #4 Crossbar Tandem (#4XB) network that was used by AT T Long Lines from its inception in the early 1940s until the 1980s when the 4ESS tandems took over This list and the historical information here is from the late telephone historian Mark Cuccia (1961-2014)
WECo Crossbar - TCI Library - Telephone Collectors Telephone Collectors International - The goal of the organization is "to educate the public, as well as the members of the Corporation, regarding the history of telephony, the value of old telephones and related items, their collectability and preservation; to research telephone history and publish and provide literature thereon; to promote the public exhibition of old telephones and related
Prologue - World Radio History Table I - Bell System toll switches, January 1, 1967 Attempts Total Systems Erlangs Hour Number No 4A crossbar 6,200 116,000 73 No 1 crossbar tandem 1,700 47,000 237 No 5 crossbar local toll 1,100* 20,000* 407 Step-by-step intertoll 330* 5,000* 500 * Nominal been expected that the special four -wire No 1 ESS might evolve into a
Survey of Telephone Switching - Chapter 8 Outgoing Sender Frame - Outgoing senders are required to complete calls, to panel offices, crossbar offices not arranged to receive multi-frequency pulsing, and manual offices arranged for panel call indicator When an outgoing trunk is selected in the 4A office to one of these offices, an outgoing sender is attached, and the trunk passes the
coldwarcomms@groups. io | Old Bell System Hierarchical US Canada Network . . . All were #4A Crossbar, except for (*) Regina SK which was a XB-Tandem 303-1 DNVRCOMA03T Denver 3 CO (June 1972) 714-1 SNBRCA0133T San Bernardino CA (Oct 1957) to the GTE central office (whether or not they FX'd to the nearest Bell ratecenter lcoal central office as well), did those local loops
Intown Central Offices - Atlanta Telephone History The 529 code was used for telephone company executive offices a No 4 ESS digital toll switching machine entered service and the 4A crossbar machine was retired This higher pitched tone was associated with No 5 Crossbar machines that were installed from around 1967 to 1972 The Buckhead 26 office was the only office in-town office
Any Switchers out There? Xbar, SxS - Classic Rotary Phones Forum We didn't use very much crossbar here in British Columbia but we did have 4A crossbar toll offices I recall the one I worked at in 1977 being very noisy during weekday business hours There always seemed to be circuits in the 4A being monitored over speakers playing the MF sounds of calls being forwarded towards their final destination
Overview of Toll Switching - Tribute to Relays A Crossbar Tandem Office, Bell Laboratories Record, Aug 1942 Myers, O , Markers for the Crossbar Toll System, Bell Laboratories Record, Aug, 1944 Survey of Telephone Switching, compiled by staff of Pacific Telephone Co, 1956, Chapter 8, 4A toll switching Swenson, P W,, Contacts, Bell Laboratories Record, Feb 1949
Western Electric Crossbar Telephone Switching Systems The new #4 Crossbar switches were called #4A (#4 Advanced) The existing #4 Crossbar switches were modified for use with the card translator – their names became #4M (#4 Modified) The #4A switches were installed between 1953 and 1968 By 1969, an electronic equivalent of the mechanical card translator system had been developed
The Telephone Historical Centre - Telephone Historical Centre The Telephone Historical Centre offers visitors an immersive look into the history of telecommunications that they can explore either on guided or self-guided tours Visitors will see everything from wooden box phones and candlesticks, classic rotary phones and working Panel and Crossbar electromechanical central office switches Many of the museum volunteers are former telephone workers