The procedures defined in this Recommendation enable telex subscribers to communicate with both packet mode and character mode data terminal equipment (DTE) connected to the PSPDN directly or via other networks. In the reverse direction, the provisions of this Recommendation enable users of packet mode and character mode DTEs, connected to a PSPDN directly or via other networks, to communicate with telex subscribers. This Recommendation applies to user classes 8-13 and 20-23 as defined in Recommendation X.1. Categories of access for DTEs accessing the PSPDN are shown in Recommendation X.10. This Recommendation does not apply to other Telematic services that may be supported by packet switched public data networks and interworking with the telex service. For example, interworking between the telex service and the teletex service or the interpersonal messaging service is not within the scope of this Recommendation. Such interworking scenarios are defined in other Recommendations.