2N Analogue GSM gateway 2N EasyGate - Manual, 1575 v1.1.0.2 - Manual (Page 66)

List of Abbreviations 6.4
66
„ SIM
Subscriber Identity Module - a chip-equipped module to be inserted in a GSM
device for identification
„ SMS
Short Message Service, a term for the system and one unit (message)
„ SW
Software
„ TTL
Transistor-Transistor Logic - a standard digital technology defining voltage for
levels 0 and 1
„ PSTN
Public Switched Telephone Network