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PROM
Programmable Read Only Memory.
Propagation Delay
The time required for a signal to travel from one end of a circuit to another.
Protocol
A set of conventions controlling the timing and format of data communications between two
pieces of communications equipment.
Protocol Convertor
Device that converts from one protocol to another.
Public Domain Software
Software from which its author has relinquished copyrights. This software is free of charge and
may be distributed for non-commercial purposes. Many bulletin boards and videotex systems
carry public domain software for users to download. See also Shareware.
Public Switched Network
Telephone system providing circuit switching to many customers.
Pulse
An abrupt and relatively short change in voltage, either positive or negative, resulting in the
conveyance of data in a circuit.
Q
Quadrature Amplitude Modulation (QAM)
A modulation technique which employs both amplitude and phase modulation to encode
multiple bits in a single element.
R
RAM
Random Access Memory.
Received Line Signal Detector
See Carrier Detect.
Redundancy Check
Technique of error detection involving the transmission of additional data related to the message
so that the receiving device can determine if the data transmitted is valid (error-free).