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Transmission Modes WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
The decoder or receiver must be tuned to obtain the midpoint between tones 5 and 6 as the center fre-
quency. In the case of IDLE (standby) transmissions these two tones are keyed at a rate of 100 ms and
tuning becomes quite simple.
Decoding of PICCOLO and COQUELET systems requires receivers with high frequency stability. Thus state-
of-the-art receivers using PLL or DDS frequency synthesis are well suited for the reception of these sys-
tems.
The software also provides an AFC (Automatic Frequency Control) function. Frequency deviations are con-
tinuously monitored by the software and automatic correction is introduced. The control range is ±5 Hz.
The AFC function may be enabled/disabled using the Demodulator menu.
The MFSK demodulator is intended for use with MFSK systems. This mode may be selected in the De-
modulator menu via the Mode item. The center frequency should be set to approximately 1700 Hz.
One manufacturer has doubled the data transfer rate and shortened the tone duration to 2 x 25 ms. this is
equivalent to a transfer rate of approximately 150 Baud Baudot with 7.5 bit codeword. The standby tones
were also changed, but otherwise the systems are identical.
Almost all transmissions in PICCOLO-MK6 and PICCOLO-MK12 are encrypted. However, some stations
transmit meteorological data and operator communication in clear.
POCSAG
The pager services introduced by a number of PTT administrations use the POCSAG (Post Office Code
Standard Advisory Group) standard. Pagers are one-way devices. A base station controls a large number
of receivers and a return channel for transmission of reception acknowledgements or text is not available.
ITA-5 with block coding, PAGER
POCSAG specifies four different call modes:
Tone only pagers (Mode 0 and 1)
The receiver can receive four different messages. The meaning of the four tones must be determined be-
forehand. The acoustic signal is supported by the display of the A, B, C or D messages on a small LCD dis-
play. All pagers must in principle have tone-only capability as a minimum.
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