The International Consultative Committee for Telephony and Telegraphy, the X.25 regulatory body.

Closed User Group.

Data Circuit-Terminating Equipment.

Data Link Escape.

Data Terminal Equipment. The user equipment (computer, terminal, etc.) connected to a network.

International Organization for Standardization.

Network Service Access Point.

Packet Assembler/Disassembler. A means of interfacing a character terminal to an X.25-based network.

Packet SwitchStream. British Telecom's X.25 Packet Switched Network (PSN).

Recognized Private Operating Agency.

Type Of Address / Numbering Plan Identification. An address format that provides increased addressing capacity suitable for communication with ISDNs.