Purpose This Standard provides performance and compatibility requirements for telephone sets intended for direct tip and ring connection to central office (CO) or private branch exchange (PBX) lines. The requirements are based on present telecommunications plant characteristics at the telephone set interface. These requirements should ensure satisfactory voice-grade service to the user in a high percentage of installations, both initially and over a period of time. However, owing to the wide range of switching equipment, customer apparatus, and loop plant (es, some subscriber carrier systems), conformance with this Standard does not guarantee acceptable performance or interface compatibility under all possible operating conditions. In general, where two levels of acceptability are specified (desirable and mandatory), compliance with the criteria in the desirable category implies a higher probability of acceptable performance or compatibility. Application These requirements apply to a telephone set intended for single-party service; however, at any one location, one or more telephone sets may be connected to the line. When multiple telephone sets are connected to a line it is assumed that only one set is off-hook at a time. If more than one telephone set is off-hook at a time, the resulting service over the network may not be satisfactory in all respects. These requirements apply also to a telephone set intended for connection to the standard station interface on a PBX as specified in CSA Standard T512 and EIA/TIA-464A. A telephone set complies with this Standard if it meets the requirements when manufactured and can be expected to continue to meet these requirements when properly used and maintained. This Standard applies to equipment for general application and selected application telephones. The latter may not be suitable in all applications, e.g., where such a telephone set is the sole instrument at a particular location. These requirements are not intended to describe specific requirements for the following types of telephones. However, the general transmission, signaling, and impedance requirements are applicable for equipment such as: (a) telephones used with data sets; (b) coin telephones; and (c) emergency special purpose telephones, or other public or semipublic telephones (eg, mine, elevator, and public emergency telephones). Limitations Electromagnetic Interference (EMI) This Standard does not include EMI requirements. User Safety This Standard does not include requirements for user safety. The applicable Standards for user safety of telecommunications terminal equipment can be found in the Canadian Electrical Code, Parts I and II, and UL Standard 1459, Standard for Telephone Equipment. Network Protection Equipment that meets the requirements of this Standard may not necessarily comply with network protection standards mandated by various levels of government. This Standard is intended to be in conformity with Part 68 of the FCC Rules and CS-03 of Industry Canada, but it is not limited to the scope of those rules.