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SoundExpression
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-zero) command
enables numeric responses. The Q1 command disables their use entirely. Example: “OK” (word),
or 0 (numeric) indicates that the modem successfully executed a command.
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