The Phone Network
Telephone System
Uses switched circuits (virtuals...).
Access via low bandwidth circuits.
“out-of-band” call establishment using signaling system based in packets (SS7).
Channels between switching exchanges carry multiple calls
Multiplexing (analogue or digital)
Public telephony (PSTN): history
1876 invention of the phone
1915 first transcontinental connection (NY–SF)
1920’s first automatic switching exchanges
1956 transatlantic cable TAT-1 (35 linhas)
1962 digital transmission (T1)
1974 Internet: voice over packets
1977 digital switching exchange
1980s Signaling System #7 (out-of-band)
1988 RDIS (ISDN Blue Book)
1990s Intelligent Networks
(1990s ATM)
2000 local bundle liberalization (Europe)
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