AT&T 2500 series Protocol converter PC, Public network, Pulse-amplitude, Modulation PAM, Q.921

GL-20GLOSSARY

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protocol converter (PC)	A device consisting of hardware, software, or a combination of both, that
	allows two systems, each using a different protocol, to communicate and
	exchange messages with each other.
public network	A network that is commonly accessible for local or long-distance calling.
pulse-amplitude	A modulation technique in which an analog signal, such as speech,
modulation (PAM)	modulates a carrier signal consisting of a series of precisely timed pulses
	of equal amplitude. See also pulse-code modulation.
pulse-code modulation	An extension of pulse-amplitude modulation (PAM) in which carrier-
(PCM)	signal pulses modulated by an analog signal, such as speech, are quantized
	and encoded to a digital, usually binary, format. See also pulse-
	amplitude modulation.
PVC	See permanent virtual circuit.
Q recommendations	Recommendations of the CCITT that affect an Integrated Services Digital
	Network (ISDN). The Q.700 series defines signaling system number 7,
	which is used for common-channel signaling across networks. Q.920 and
	Q.931 define a digital-access signaling system for signaling between the
	customer’s equipment and the network. See also CCITT, Q.920 and
	Q.921, and signaling system number 7.
Q.920 and Q.921	The level-2 (data-link layer) specification for use in an Integrated Services
	Digital Network (ISDN) recommended by the CCITT for message
	transmission. See also Q recommendations.
Q.930 and Q.931	The D-channel level-3 (network layer) specification for use in an
	Integrated Services Digital Network (ISDN) recommended by the CCITT
	for basic telecommunications call control. See also codepoint and D-
	channel.
remote access trunk	A telecommunications channel used by an authorized user to gain access
	to the communications system.
restricted [channels]	Restricted channels are channels over which no all-zero bytes can be
	transmitted. The line equipment transmitters on restricted channels use
	ZCS line coding.
RNX	The location code for a private-network communications system, where R
	equals any digit 2 through 9 except the assigned call-detail recording
	(CDR) account code prefix, N equals any digit 2 through 9, and X equals
	any digit 0 through 9.
robbed-bit signaling	Digital signal level-1 (DS1) signaling in which up to eight kbps from each
	of the 24 64-kbps channels are used for signaling in every sixth frame.
	The least-significant bit of each 8-bit sample is replaced by a signaling bit.
	Also called DS1 robbed-bit signaling.