Telenetics 56 - Manual (Page 148)

AT Commands
Page 140
received from the remote is discarded. If the modem detects a DTR drop while &D2 is in
effect, it goes on-hook, sends <DLE><ETX> to the DTE, generates OK result code, and
returns to command mode. If the modem detects a DTR drop while &D3 is in effect, the
modem performs a warm reset.
Fax Data Transmission
Fax data transmission is initiated by the AT+FTM=<mod> command. After this
command is issued, the modem generates the CONNECT message and transmits carrier
in the modulation scheme specified by the parameter n. The modem then transmits
constant 1 bits for a minimum of one second and continues to transmit constant 1 bits
until it receives a character from the DTE.
When data is received from the DTE, the modem deletes start and stop bits and deletes all
<DLE><chr> character pairs before transmitting the data to the remote. Each
<DLE><DLE> sequence is transmitted as a single <DLE>. <DLE><ETX> is considered
As the end of stream maker, and is not transmitted. All data received from the DTE after
the <DLE><ETX is ignored by the modem until the modem generates either the
CONNECT, or OK, or ERROR result code.
If no more data is in the transmit buffer, and the last transmitted character was not an
ASCII NULL, the modem generates the OK result code and returns to the command
mode. If the last character transmitted was an ASCII NULL, the modem generates the
CONNECT message to the DTE and waits for further data from the DTE while
transmitting NULLs to the remote. If more data is received before five seconds elapse,
the modem continues to transmit the data as described in the previous paragraph. If five
seconds elapse and no data is received from the DTE, the modem drops carrier, goes on-
hook, and generates the ERROR result code.
Fax Data Reception
Fax data reception is initiated using the AT+FRM=<mod> command. After this
command is issued, the modem looks for carrier in the modulation scheme specified by
the parameter n. If no carrier is detected before the period of time specified by register S7
expires, the modem generates the NO CARRIER message and returns to command
mode. If a V.21 carrier is detected when a high speed carrier is expected, the modem
generates the +FCERROR message and returns to the command mode. If the specified
carrier is detected, the modem generates the CONNECT message and enters the data
receive mode.
While in data receive mode, the modem receives data from the remote, adds start and
stop bits, and handles <DLE><chr> character pairs before passing the data to the DTE. The modem
prefixes each <DLE> character with another <DLE> character before sending it to the DTE.