Black Box MD1640A Modem User Manual


 
90
SERIES II INTELLIGENT DATA/FAX MODEMS
Force Answer Mode A
You can force the Series II Modem into Answer mode with the modem’s
A command.
Entering ATA when in Command mode immediately brings your mo-
dem off-hook, out of Command mode and into On-Line Answer mode,
and causes it to transmit its carrier signal over the phone line. If no
responding carrier tone is received by your modem within forty-five
seconds (or some other time as determined by S-Register S7), your
modem stops transmitting its tone, hangs up, and goes back into
Command mode.
Exiting Command Mode, Going Back On-Line O
You can bring the Series II Modem out of Command mode and back
into On-Line mode by entering ATO (where O is the letter O, not the
number 0). In this case, the O command reverses what was done by
entering the Escape Code. The O command will bring the modem into
the same On-Line mode (Originate or Answer) that it was in prior to
going into Command mode.
5.4.13 Line Probe Commands
Before V.34 negotiation takes place, remote and local modems transfer
their functional capabilities using modulated calling and answering
tones; indicating the common capabilities of the modem at each end.
Once this is done, a probing signal is passed between the modems to
identify impairments in the telephone channel (e.g., Receive Signal
Strength vs. Frequency, Noise vs. Frequency and Signal to Noise Ratio
vs. Frequency). After receiving the results of the probing signal, the
modem receivers and transmitters begin with the lowest speed and
move up until reaching the highest speed at which they can exchange
data. All this occurs in about five seconds.
There are a number of Line Probe Commands. These commands are
configurable and can be stored to RAM (via AT&W0).