Introduction Revision C of EIA/IS-3 introduced the facility of ??extended protocol?? where neither the coding nor use of the message type was standardized. The extended protocol facility usage was standardized by TIA-691 and is also indirectly referenced by TIA/EIA/IS-2000.6. In addition@ the extended protocol facility allowed for proprietary implementations through the reservation of Message Type Codes. To avoid confusion resulting from multiple assignments@ the Committee recognized the need to provide a single master list of the message type codes that have been registered for the analog air interface. Manufacturers or others wishing to register non-standardized use of particular message type codes should refer to section 3 of this document.