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Pol-arq, Press-fax – Wavecom W-SPECTRA (Automatic Monitoring System) V1.1.0 User Manual

Page 165

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WAVECOM Monitoring System W-SPECTRA, W-SPEED Manual V1.1.0

Transmission Modes

155

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.

PRESS-FAX

The transmission of press fax images on short-wave is based on gray levels and specific IOC values. A
number of IOC assignments were modified for press image transmissions. These special characteristics are
taken into account in the PRESS-FAX software.

Parameter

Value

Frequency range

HF

Operation modes

Graphic mode, Broadcast

Center frequency

1900 Hz

Speed

60, 90, 120, 180 and 240 RPM, IOC 288, 352 and 576

Receiver settings

FAX, DATA, CW, LSB or USB

Input format(s)

AF, IF