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18
20-90 VHF & UHF TRANSCIEVER
Product Manual
Sea Air and Land Communications Ltd, 10 Vanadium Place, Addington, Christchurch 8024, New Zealand
September 2021
POCSAG Rapid
POCSAG rapid allows a faster response to a push button input. POCSAG rapid uses a short
preamble, and starts the message transmission in the first POCSAG frame, regardless of the CAP
code. For even faster response, keep messages short, use numeric or tone only messages, reduce
the de-bounce time, and consider using 1200 or 2400 baud.
The transmitted CAP code will be a multiple of 8. The POCSAG frame number is part of the full
CAP code, and POCSAG rapid always starts in frame 0.
POCSAG rapid would be used without “while held” for separate “open” and “close” buttons.
While Held
The “While Held” option sends messages continuously while the input is in the specified state.
When used with POCSAG rapid, messages are transmitted continuously in all eight frames of the
POCSAG data stream, until the input is released. This allows the receiver to use a short mono-shot
timer on the output, providing quick push-button release response (momentary action).
The transmitted CAP code will be a multiple of 8 plus the slot position, from 0 to 7. A long enough
transmission will cycle through all 8 CAP codes the start over. A receiver should be configured to
respond to all eight CAP codes.
Mono-shot Delays
The fastest release response can be achieved by reducing the mono-shot delay to the minimum
required to guarantee that the output will be retriggered before the mono-shot times out.
Minimum delays (seconds) are as follows:
Message type
512 Baud
1200 Baud
2400 Baud
Tone only:
Output defined by
CAP code range
0.150
0.075
0.050
Numeric:
Relay protocol, up to
10 digits
0.275
0.150
0.075
Alpha-numeric:
Relay protocol, up to
14 characters.
0.400
0.175
0.100
Note: POCSAG rapid is not intended to work with pagers.