Technical informations - Systems

Flex / REFlex - Flexible wide area paging protocol
Si tratta di un nuovo sistema Pager sviluppato nel 1994 da Motorola. Opera su un canale a 12.5, 25 o 50 kHz con velocitÓ di 1600, 3200 e 6400 bps, modula il segnale con 2/4 livelli FSK. La disposizione dei 4 toni Ŕ normalmente -4800 -1600 0 1600+ 4800+ Hz.

Paging protocol introduced by Motorola late in 1994 and will be the protocol of choice as paging company upgrade from POCSAG to FLEX in the US. FLEX supports rates of 1600, 3200 and 6400bps and can handle up to 5 billion addresses. FLEX has a 4 frequency signal arranged as evenly spaced tones with usual shifts (in Hz) of: -4800/-1600/ +1600/+4800. This signalling technique is also more susceptible to noise so a robust error correction scheme is incorporated. FLEX pagers also appear to have a decreased effective paging radius when compared to POCSAG. FLEX is a synchronous time slot protocol. The FLEX protocol does not send messages at random but instead sends all paging data destined for a particular pager during a pre-defined time slot. The pager only wakes up only when a message is expected to arrive in real time thereby saving battery life.