The GSM logo is used to identify compatible working of gsm module sim900 pdf and equipment. The dots symbolize three clients in the home network and one roaming client. Europe, and EU rules were passed to make GSM a mandatory standard.
The decision to develop a continental standard eventually resulted in a unified, open, standard-based network which was larger than that in the United States. In February 1987, Europe produced the very first agreed GSM Technical Specification. The MoU drew in mobile operators from across Europe to pledge to invest in new GSM networks to an ambitious common date. 900 MHz spectrum band for GSM. Work began in 1991 to expand the GSM standard to the 1800 MHz frequency band and the first 1800 MHz network became operational in the UK by 1993, called and DCS 1800.