67
long space disconnect
. Determines whether
or not modem disconnects when it receives a
continuous break from a remote modem.
Controlled by the ATY command.
loopback tests
. There are four types of
loopback tests which are as follows: (1) the
local digital loopback tests the operation of
the DTE, including whether or not data is
leaving the terminal or computer port; (2) the
local analog loopback tests the digital and
analog circuits of the modem; (3) the remote
digital loopback checks the operating
condition of the line and remote modem; (4)
the remote analog loopback tests the line to
the remote modem.
M
MNP
. Microcom Networking Protocol. A
series of data communications protocols
developed by Microcom for full-duplex, error-
free communications.
make/break ratio
. The &P command controls
the ratio of the off-hook (make) to on-hook
(break) interval used by the modem when it
pulse dials. &P0 selects a 39%/61% make/
break ratio for use in the U.S. &P1 selects a
33%/67% make/break ratio for use in the
United Kingdom and Hong Kong. The &P
command is NOT allowed in some countries.
modulation handshake
. Also referred to as
Automode Enable and is controlled by the
ATN command. This determines whether or
not the modem must connect at a particular
speed, or allow connection at any speed
supported by both modems.
N
negotiation fallback
. Controlled by S-
Register 36 as part of the V.42 protocol.
Setting this register indicates what action to
take when a desired connection cannot be
made (e.g., hang-up, direct mode connect,
normal mode connect).
non-volatile RAM
. Also NVRAM. Random
access memory whose data is retained when
power is turned off. This is especially useful
for modems to store user-defined default
configuration settings and frequently used
telephone numbers. This information would
be loaded into modem RAM at power-up.
O
on-line state
. Same as data mode. To transmit
or receive data, the modem must be in the on-
line state. When placing a call, the modem is
put on-line with the dial command.
P
PBX
. Private Branch Exchange. A telephone
switch at a customer site.
pulse dialing
. Also referred to as rotary
dialing, i.e., dialing with the older-style rotary
dial wheel. The dial modifier ATDP sets the
modem to pulse dialing, which is the default
method as opposed to tone dialing (push-
button touch-tone) which is enabled with
ATDT. All telephone exchanges will accept
older-style pulse dialing and most exchanges
will accept modern tone-dialing. Tone dialing
is faster and more reliable since mechanical
relays and their inherent failure mechanisms
are avoided.
R
result code
. A response sent by the modem
after executing a command. The response
reports the modem’s status or the progress of
a call and can take the form of either digits
(numeric) or words (verbose). Issuing a V1
command enables word responses. A V0 (V-
Glossaries
