WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0 Modem and FAX Modes
315
Protocols
T.4 mono-dimensional, bi-dimensional
Input and interfacing
The fax and modem decoder accepts input sampled at 8 kHz with a precision of ± 0.01% and stored into a
signed 16 bit linear format. The dynamic range of the input shall not exceed 12 bits + 1 sign bit.
One or two sampled streams are accepted, depending on the capture method being mono-directional or
bi-directional.
The input may be a samples file in the format listed below:
 16-bit signed linear
 8-bit signed linear
 8-bit unsigned linear
 A-law
 A-law inverted
 Mu-law
 Mu-law inverted
The decoder will accept fax and modem signals using the AF input. Full-duplex requires two channels (ste-
reo).
In order to interface to a telephone line an adapter blocking the line and ringing voltages to the decoder,
but passing through these voltages to the devices must be employed. To capture signals the decoder must
be inserted between the calling and the called device.
The actual configuration of the interface adapter will depend on the type of telephone line, the value of
line and ringing voltages, local laws and regulations and physical connectors used - line adapters should
be acquired locally.
Constraints
If only mono-directional capture is available, the following demodulation constraints apply:
T.30 (V.21 modulated) – Signals from recorded direction demodulated; opposite direction demodu-
lated if echo level is sufficient.
V.22/V.22bis – Signals from recorded direction demodulated; opposite direction demodulated if
echo level is sufficient.
V.32/V.32bis – Signals from recorded direction demodulated if echo from opposite direction is suf-
ficiently low.
V.34/V.90 – Demodulation impossible.
The recording must include all signaling from the very beginning of a transmission otherwise demodulation
and decoding may not be possible. Carrier lost or reception of fax DCN signal is considered as the end of
communication.
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