Zetron Simulcast Paging System
The Zetron High Speed Simulcast Paging System consists of one M600 unit and multiple M620 units. Both the M600 and the M620 use the RTEMS operating system running on a Motorola MPC860.
We have had units in the field for well
- ver a year (as of January 2004). The only failure so far was due to a lightning strike on a unit
that was not correctly protected. The OS has worked reliably and without any problems. The following is a brief description of what the system does.
Zetron's High Speed Simulcast Paging System employs a single Source Unit (Model 600 Wireless Data Manager) and multiple (up to 1000) Destination Units (Model 620 Wireless Data Encoders). The units are all equipped with GPS receivers, and their time base is synchronized to within 1 microsecond. This is a complicated system with multiple units transmitting the same data from multiple sites, and the bit edges from each transmitter are aligned to within +/- 500ns (using a GPS receiver at each site for time reference). The bit alignment is done using RTEMS-managed interrupts and the 860's onboard timers.
The Model 600 receives pages from a paging terminal or similar device. The Model 600 then very accurately determines the exact time (plus or minus one microsecond) the pages should be sent. The Model 600 creates data packets that it sends to the Model 620 Destination Units. These data packets contain the paging data and the time stamp indicating when to send the data for
- ptimal simulcast coverage.
Every remote transmitter in the paging system is connected to a Model 620 Wireless Data Encoder. At the precise time indicated by the attached time stamp, the encoded message batch is sent to the transmitter, resulting in a broadcast transmission precisely synchronized with other Model 620-controlled transmitters.
This application was reported by Phil Torre (ptorre AT zetron DOT com).