Communications engineering. International standard for the second generation of mobile communication systems. Transmission frequencies are 900 MHz, 1800 MHz and 1900 MHz. The data transfer rate is 9.6 Kbit/s. GSM is the worldwide most used mobile phone standard for telephony, data transmission (both packet and circuit switched) and short message service (SMS). The digital standard GSM was developed as the successor of the analog first generation of mobile communcation systems (1G, in Germany representative for the A, B and C nets).