Also known as: POCSAG
POCSAG (the CCIR Radiopaging Code No. 1) is the classic one-way paging protocol used worldwide to deliver numeric and alphanumeric messages to pagers. It is a simple asynchronous 2-level FSK scheme, still in active use by hospitals, fire/EMS, and industry.1
Overview
A POCSAG transmission begins with a preamble and sync codeword, then batches of address and message codewords. Each pager listens for its address (capcode). Messages are protected by a BCH(31,21) code plus a parity bit.
Technical characteristics
| Property | Value |
|---|---|
| Modulation | 2-FSK (±4.5 kHz typical) |
| Bit rates | 512, 1200, 2400 bps |
| Coding | BCH(31,21) + even parity |
| Content | Numeric or alphanumeric |
History
Developed by the British Post Office and standardised by the CCIR in the early 1980s; it became the dominant global paging code.1
Deployment
Hospitals, emergency services, and industrial paging; the amateur DAPNET network also uses POCSAG.
Decoding it with GopherTrunk
GopherTrunk demodulates the FSK, recovers codewords, and decodes numeric/alphanumeric messages. See the POCSAG decoder page.