Multitech MMH900 User Manual page 191

Phase: The timing of a signal based upon
the starting point of each cycle in another
signal. To be detected phase requires the
comparing of two signals. If the cycle of two
signals begin at the same point, they are said
to be "in-phase". In-phase signals add, while
out-of-phase signals tend to cancel each
other.
Port: A location for input or output data
exchange. Computers, muxes, etc. have
ports for various purposes.
Program: A collection of computer instruc-
tions that tell the computer what to do.
PROM (Programmable Read Only
Memory): (pronounced "prom") A
permanent memory chip that can be pro-
grammed or filled by the customer after by the
manufacturer has set initial values. Contrast
with ROM.
Prompt: A request for information from the
PC that provides required input or information.
Protocol: A set of rules that defines how
computing devices communicate with each
other. The rules governing the transmitting
and receiving of data.
PSTN (Public Switched Telephone
Network): A worldwide public voice tele-
phone network that is used as a telecommuni-
cations medium for the transmission of voice,
data and other information.
Pulse dialing: One of two methods of dialing
a telephone, usually associated with rotary-
dial phones. Compare with tone dialing.
Pulse-width: This pertains to a digital signal.
Pulse width refers to the duration of one state
between clocking signals. Pulse width roughly
corresponds to an analog signal's wavelength.
Q
Queue: A set of activities that are waiting in
chronological order for an action, such as
printing, to be performed.
R
Rack: A frame or cabinet into which
components are mounted. The industry
standard rack is 19" wide and has variable
depth and height.
Rackmount: A packaging style available for
many types of electronic equipment which
enables the installer to mount the equipment
in an industry standardized enclosure. The
rackmount equipment is fitted with brackets,
rather than being packaged in its own
enclosure. Rackmounting conserves disk or
floor space (real estate) and often conserves
power outlets.
RAM (Random Access Memory) (pro-
nounced "ram"): A computer's primary
workspace. All data must be stored in RAM
(even for a short while), before software can
use the processor to manipulate the data.
Before a PC can do anything useful it must
move programs from disk to RAM. When you
turn it off, all information in RAM is lost.
RJ-11: An industry standard interface used
for connecting a telephone to a modular wall
outlet; comes in 4-and 6-wire packages.
RJ-45: An 8-wire modular connector for voice
and data circuits.
ROM (Read Only Memory) (pronounced
"rom"): A memory chip that permanently
stores instructions and data. Its contents are
created at the time it is manufactured and
cannot be altered. ROM is used to store
control routines in PCs and peripheral
controllers. ROM is also used in the plug-in
cartridges for printers and video games. A set
of ROM chips contain the basic input/output
system (BIOS).
RS232-C: An EIA standard for a serial
interface between computers and peripheral
devices (modem, mouse, etc.). It uses a 25-
pin DB-25, or a 9-pin DB-9 connector. The
RS-232 standard defines the purposes,
electrical characteristics and timing of the
signals for each of the 25 lines.
RTS (Request To Send signal): With
communications between modems, an RS232
signal sent from the DTE to the modem
requesting permission to transmit. Contrast
with CTS.
S
Serial Port: The connector on a PC used to
attach serial devices (those that need to
receive data one bit after another), such as a
mouse, a printer or a modem. This consists
of a 9- or 25-pin connector that sends data in
sequence (bit by bit). Serial ports are referred
to as "COMx" ports, where x is 1 to 4 (i.e.,
COM1 through COM4). A serial port contains