The Nortel SP1 4-Wire was an early electronic switch used as a Class 4 switch.
telephone | Gym Class Heroes | Telephone tapping | class action | Plain old telephone service | class | Class A | working class | Switch | Nippon Telegraph and Telephone | Railroad switch | DB Class 218 | Class War | British Rail Class 37 | Social class | British Rail Class 47 | Victorian Railways X class | switch | GWR 3031 Class | Class D | British Rail Class 66 | World Class Championship Wrestling | Telephone exchange | telephone exchange | Saved by the Bell: The New Class | railroad switch | Premium-rate telephone number | Nimitz-class aircraft carrier | Middle Class Rut | Middle class |
The first Class 5 switch, the DMS-10, began service on 21 October 1977 in Fort White, Florida and the first toll switch (Class 4), the DMS-200, entered service in 1979 in Ottawa, Canada.