Wavecom W61PC V7.5.0 - Manual (Page 211)

WAVECOM Decoder W61PC/LAN Manual V7.5 Transmission Modes  201
The synchronization word is followed by eight frames (frame 0 - 7) containing 2 x 32 bits in total. Only the
first 32 bits are however used for transmitting a pager address. It would therefore be possible to double
the maximum number of subscribers in the group by utilizing the frame contents to its full extent.
The message contents of the code words may include pager addresses or messages destined for specific
pager addresses. The frames contained in a batch are numbered from 0 to 7. All pagers are similarly di-
vided into 8 groups with each pager only receiving frames for the group to which it has been assigned. A
pager synchronizes itself to the batch synch codeword (SC) and ignores the seven frames which are not
applicable.
Following the address at the beginning of a frame, a message of any desired length may be sent. In the
case of numeric pagers, digits are sent in BCD code while for alphanumeric pagers the message is trans-
mitted using 7 bit ASCII codes.
The example shows the transfer of a message of 350 bits in frame 3. The first 32 bits of frame 3 are the
address codeword (Add). Then follow 4 1/2 frames equivalent to 9 x 32 bits which extend up to the next
synch word (SC). The remaining 62 bits fit into frame 0. If the frame containing the end of a message is
not required to send a new address, it is filled with IDLE codes until a new address or a new synch word
must be sent.
POCSAG mode uses direct frequency modulation. Proper decoding is only possible from the receiver IF
output.
POL-ARQ
POL-ARQ is a full-duplex system with two transmitting frequencies. The system is based on the SITOR-
ARQ alphabet. This alphabet having a 4:3 mark-space ratio allows error detection. Like all duplex systems,
POL-ARQ initiates a request for repetition cycle (RQ) when transmission errors occur.
Parameter Value
Frequency range HF
Operation modes Duplex ARQ
Modulation FSK
Symbol rate 100, 150 and 200 Bd, variable 30-650 Bd
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
POL-ARQ operates at a symbol rate of 100 and 200 Bd on the radio link.
To synchronize to this mode select a baud rate. By selecting the Auto button, the automatic determina-
tion of center frequency, shift frequency and baud rate is performed. Signal polarity (LSB or USB side-
bands) is automatically detected.
To maintain synchronization between the two duplex stations, both transmitters operate continuously. If
no data is transmitted an idle bit pattern is sent.
At 100 Bd the last three characters are repeated after the RQ character. At 200 Bd the last four characters
are repeated (5 character repetition cycle). Due to mode characteristics the character repetition cycle
must be controlled manually.