ERMES

The Enhanced Radio Message System (ERMES) is a paging technology defined by the European Telecommunications Standards Institute (ETSI). ERMES has many advantages over the existing POCSAG systems in Europe. It operates in a frequency range that is common throughout Europe. This allows subscribers to roam throughout Europe and still receive pages.

ERMES transmits the data at a speed of 6,250 bit/s. ERMES uses Frequency Shift Keying (4-FSK) modulation. The transmission are divided in 60 cycles of 1 minute in length. Each cycle is divided into 5 subsequences of 12 seconds. Each subsequence is further divided into 16 batches, labeled A through P. The pager population is divided into 16 groups, each being allocated to one of the 16 batches. The pager has only to be active during the period it has been allocated to. This extends the battery life of the pager.

Originally, the ERMES frequency band consisted of 16 channels of 25 kHz within the 169,4125-169,8325 MHz frequency range. In 2006 the number of channels was brought back to 8 channels because ERMES was not as successfull as hoped for.

Each pager scans all frequency channels to allow for modification of the network without the need to modify the pager settings.