There are two modes:
command mode and data mode. When both modems are on-hook conditions, it is the
command mode. After call-originating PC receives "C" after the start
dialing command, it becomes the data mode. The call-originating PC must send
"C" to the answering modem as soon as it receives "C" from
the answer modem so that the answer modem transmits "C" to the other
PC to indicate that modems are connected each other.
Telephone number
entry command: D+(new telephone number)(CR)
Note: CR is a
carriage return (hex D) or ENTER.
Example: D18005551212
for setting a telephone number for 18005551212.
Start dialing
command: G
Note: CR is not
required after G.
Abort command to
return to on-hook condition during command mode: A
Note: CR is not
required.
On-hook command: command
to return to on-hook condition during data mode: +++
Note: override condition to ignore the abort
command is obtained by
KAE01MF202KAE00 during command mode. There is
acknowledge character, C, is returned by LS15.
On-hook timeout: timeout
timing to return to on-hook automatically: 30 seconds from the end of dialing
sequence, the end of data transmission, or answering ring signal. The timing
may be changed by:
KAE01MF3(n1)(n2)KAE00 where n1 and n2 forms hexadecimal number with each count
is equal to two seconds. For example, KAE01MF307KAE00 would change to fifteen
seconds time out. Thirty seconds is default vale.
Status characters:
C to indicate that
the other modem has answered the call.
F to indicate that
called modem is busy, or no loop current.
O to indicate that
line becomes on-hook whenever a modem goes on-hook after receiving disconnect signal
(loss of loop current), on-hook time-out, or on-hook command (+++).
Modem specifications:
Baud rate: 1200
half-duplex
FSK with 1200Hz
(mark) and 2200 (space)
Half-duplex time-out:
2 seconds. When a transmitting modem does not transmit character for more than
two seconds, the carrier signal is turned off. Modems wait for either input at
RS232 of carrier signal from other modem. When a modem receives input at RS232
interface, carrier (mark signal) is turned on. It waits for 500 ms and the
character is transmitted. Then any input character is transmitted immediately. Therefore,
it must have delay for 500 ms between first and second input.
Micro Seven, Inc.
10-21-07