Multi-Tech Systems MVP120 - Manual (Page 98)

PRI (Primary Rate Interface): Used on ISDN. In North America, and Japan, PRI is one 64Kbps D channel and 23 B channels.
Elsewhere, it is one D channel and 30 B channels. PRI is the ISDN equivalent of a T-1 circuit.
Primitive: An abstract representation of interaction across the access points indicating that information is being passed between
the service user and the service provider. The OSI Reference Model defines four types of primitives: Request, Indication, Response
and Confirm.
PROM (Programmable Read Only Memory - pronounced "prom"): A permanent memory chip that can be programmed or filled
by the customer after by the manufacturer has set initial values. Contrast with ROM.
Protocol: 1. A set of semantic and syntactic rules that determines the behavior of functional units in achieving communication. 2.
In Open Systems Interconnection architecture, a set of semantic and syntactic rules that determine the behavior of entities in the
same layer in performing communication functions. 3. In SNA, the meanings of and the sequencing rules for requests and re-
sponses used for managing the network, transferring data, and synchronizing the states of network components. 4. Synonymous
with line control discipline.
PSTN (Public Switched Telephone Network): A worldwide public voice phone network that is used as a telecommunications
medium for the transmission of voice, data and other information.
Public Data Network (PDN): A packet-switched network that is available to the public for individual ("subscriber") use. Typically,
controlled by a government or a national monopoly.
Public Switched Telephone Network (PSTN): The group of circuit-switching voice carriers, which are commonly used as analog
data communications services.
Pulse Code Modulation (PCM): 1. In data communication, variation of a digital signal to represent information; for example, by
means of pulse amplitude modulation (PAM), pulse duration modulation (PDM), or pulse position modulation (PPM). 2. Transmis-
sions of analog information in digital form through sampling and encoding the samples with a fixed number of bits.
Pulse dialing: One of two methods of dialing a phone, usually associated with rotary-dial phones. Compare with "tone dialing".
Q
Quality of Service (QoS): Guarantees network bandwidth and availability for applications.
Quantizing: The process of analog-to-digital conversion by assigning a range, from the contiguous analog values, to a discrete
number.
R
Random Access Memory (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.
RAS Channel: An unreliable channel used to convey the Registration, Admissions and Status messages and bandwidth changes
between two H.323 entities.
Rate Enforcement: The concept in frame relay where frames sent faster than the CIR are to be carried only if the bandwidth is
available, otherwise they are to be discarded. (The frame relay network assumes that anything exceeding the CIR is of low priority.)
Rate enforcement makes sure that the network will not get so congested that it isn't able to meet the agreed on CIR
Recognized Private Operating Agency (RPOA): A corporation, private or government-controlled, that provides telecommunica-
tions services. RPOAs, such as AT&T, participate as non-voting members in the CCITT.
Red Alarm: A T1 error condition generated when a local failure (e.g., loss of synchronization) exists for 2.5 seconds, causing a
Carrier Group Alarm (CGA). See also "Blue Alarm" and "Yellow Alarm".
Request for Comment (RFC): A set of papers in which Internet standards (published and proposed), along with generally-
accepted ideas, proposals, research results, etc. are published.
Ring Down Box: A device that emulates a CO by generating POTS calls for testing and product demos.
Ring Down Circuit: A tie line connecting phones where picking up one phone automatically rings another phone. A feature used
for emergencies to alert the person at the other phone of the incoming call.
RJ-11: An industry standard interface used for connecting a phone to a modular wall outlet; comes in 4-and 6-wire packages.
RJ-45: An 8-wire modular connector for voice and data circuits.
Robbed Bit Signaling: The popular T1 signaling mechanism where the A and B bits are sent by each side of the T1 termination
and are "buried" in the voice data of each voice channel in the T1 circuit. Since the bits are "robbed" infrequently, voice quality is
remains relatively uncompromised. See "bit robbing".
The robbed-bit signaling technique is used in D4 channel banks to convey signaling information. The eighth (least significant) bit of
each of the 24 8-bit time slots is "robbed" every sixth frame to convey voice-related signaling information such as on-hook, off-
hook, etc., for each channel.