Jabarkan Electronic switches dari Sentral telepon dalam bahasa sunda

The first Electronic Switching Systems were not entirely digital. The Western Electric 1ESS switch still had reed relay metallic paths. It was stored-program-controlled.  Equipment testing, changes to phone numbers, circuit lockouts and similar tasks were accomplished by typing on a terminal.  Northern Telecom SP1, Ericsson AKE, Philips PRX/A, ITT Metaconta, British Telecom TXE series and several other designs were similar.  These systems could use the old electromechanical signaling methods inherited from crossbar and step-by-step switches.  They also introduced a new form of data communications: two 1ESS exchanges could communicate with one another using a data link called Common Channel Interoffice Signaling, (CCIS).  This data link was based on CCITT 6, a predecessor to SS7.