tandard Because the data is being sent across a digital air interface, no modem is required at the mobile station (MS) end. Supplementary Services Supplementary services (which are really the added features of the cellular networks) are provided on top of teleservices or bearer services, and include features such as Caller identification. Call forwarding; the subscriber can forward incoming calls to another number if the called mobile is busy (CFB), unreachable (CFNRc), or if Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Introduction to GSM Introduction to GSM no reply (CFNRy) occurs. Call forwarding can also be applied unconditionally (CFU). Call waiting. Multiparty conversations. Barring of outgoing (international) calls. Different types of call barring services are available: Barring of All Outgoing Calls (BAOC) Barring of Outgoing International Calls (BOIC) Barring of Outgoing International Calls except those directed toward the Home PLMN Country (BOIC-exHC) Barring of All Incoming Calls (BAIC) Barring of Incoming Calls when Roaming (BAIC-R) Phase II enhancements to the supplementary services include the following: Calling/Connected Line Identification Presentation (CLIP) This supplies the called user with the ISDN of the calling user. Calling/Connected Line Identification Restriction (CLIR) This enables the calling user to restrict the presentation. Connected Line identification Presentation (CoLP) This supplies the calling user with the directory number he or she receives if his or her call is forwarded. Connected Line identification Restriction (CoLR) This enables the called user to restrict the presentation. Call Waiting (CW) This informs the user, during a conversation, about another incoming call. The user can answer, reject, or ignore this incoming call. These are added supplementary services finishing off the list: Call hold Th