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The TeleZapper is an appliance that plugs into a consumer telephone line. On detecting a ring and answer of any phone on the line, the Telezapper will immediately play a sequence of Special information tones or "SIT": one of eight internationally standardized signals that indicate a call cannot be completed. Typically the "Intercept" or "IC ...
The Number Five Crossbar Switching System (5XB switch) is a telephone switch for telephone exchanges designed by Bell Labs and manufactured by Western Electric starting in 1947. It was used in the Bell System principally as a Class 5 telephone switch in the public switched telephone network (PSTN) until the early 1990s, when it was replaced ...
EMS-1 (The ITEC Electronic Modular Switch is an electronic direct control switching system. The modules are combined to form a complete switch or any of the modules can be added to your present Step-by-Step Systems.) EMS-2 (The EMS-2 RURAL SWITCH is a stored program control analog switch designed to be cost-effective in small exchanges.
A dial tone (dialling tone in the UK) is a telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone, when an off-hook condition is detected. It indicates that the exchange is working and is ready to initiate a telephone call. The tone stops when the first dialed digit is recognized.
The protocol was introduced in the Bell System in the United States by the name Common Channel Interoffice Signaling in the 1970s for signalling between No. 4ESS switch and No. 4A crossbar toll offices. [1] [2] The SS7 protocol is defined for international use by the Q.700-series recommendations of 1988 by the ITU-T. [3]
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The No. 4 Electronic Switching System (4ESS) is a class 4 telephone electronic switching system that was the first digital electronic toll switch introduced by Western Electric for long-distance switching. It was introduced in Chicago in January 1976, to replace the 4A crossbar switch. [1]