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Low-Level Modem Command Dictionary
to be mutually exclusive. No data will be transmitted or received in this state. Since changing to
VOICE
mode halts any carrier tone being issued by the modem, and the remote modem will end its
carrier when the HP 827l8A's is lost, the data communication session will end, and the unusual
response will revert to the form
ONV
shortly after it appears.
Responses: see above
R (REDIAL)
R
[dial string]
t'10DOUT
II
~.~p
I
9~'~
1
(:::[1[1)
555-1212
II
:~.:CHP$
( 1:::::'
Redials the last dialed number. Behaves exactly like the 0 (DIAL) command unless the called phone is
busy. Then, instead of hanging up after reporting the
BUSY
response, the
R
command automatically
redials the
dial string
at intervals of about 40 s until the number is not busy, or until ten dials have
been attempted. See the D command for further details and for the syntax of a
dial string.
You can string multiple R commands together (up to 10, as described for the 0 command) to redial up to
100 times.
Responses: 0, 1, 2, 3, 5, B
T (TEST)
I
T test number
t'10DOUT
II
\T
111
g.:CHP$ ( 1 :::::.
Instructs the modem to perform self -tests. The
test number
is a single digit
(0- 2)
that specifies one of
three different tests. The modem mode and parameters are not affected by any of the different tests,
except that the data in the transmit and receive buffers may be lost, and the modem will be on-hook after
test 1 is completed,
Test 0 is the hardware integrity test. The modem goes on - hook and executes the power-up self -test. As
when the modem is turned on, the modem will report
OK
if the self -test is successful (the
OK
reported
after a command is executed, not the special
OK
reported when the modem is turned on). If the test fails,
the FAIL response is reported, and the test is repeated. The test will continue to report FAI L and will be
repeated until the modem is turned off or the test passes.
Test 1 is the analog loop back test. The modem goes off - hook, connects its analog output to its analog
input, and switches the receive circuitry so that it receives and transmits in the same frequency band.
The modem will route all data through its analog circuitry and back to the HP-75 (actually echoed into
the receive buffer for
t'10D I
t'~$
to read) until it receives any low-level modem command.
Test
2
is the local digital loopback test. The modem goes off -hook and retransmits any data that it
receives over the phone line. Data from the HP-75 will be ignored. If the modem is in
MODEM
mode, it
tries to establish a data connection by issuing either an answer or an originate tone, depending on whether
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