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Transmission Modes WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
In most systems the accuracy of the single frequencies has to be within +1/-1.5% of the nominal value.
If a DTMF call is received, the call sign is displayed on the monitor. In the Options menu a Time stamp
function can be enabled to add date and time to each call.
Tone Allocation
Tone duration: 70 ms.
DUP-ARQ
DUP-ARQ is a semi-duplex system. The radio channel is used by a DUP-ARQ system in the same way as a
simplex system, both stations alternating in transmitting blocks of five characters and a Hamming check-
sum. If a transmission error occurs a repeat request is initiated and the last data block is re-transmitted.
125 Bd, variable 30-650 Bd
DUP-ARQ operates at a Symbol rate of 125 Bd on the radio link.
If only one station is sending data, the other station transmits an IDLE pattern and initiates RQ cycles in
case of transmission errors.
DUP-ARQ has automatic channel selection facilities. Before transmission starts, the best available short-
wave transmission channel is selected and its quality is continuously checked for the duration of the
transmission. Within a given frequency range the system may select one of 5 possible channels which are
spaced at 400 Hz intervals. Because of this channel selection mechanism, the two linked stations may
transmit at different frequencies.
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