User manual

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