| Field | Communications |
| Went Obsolete | 1980s in most areas of the USA |
| Made Obsolete By | Electronic Switching |
| Knowledge Assumed | Verbal communications and location and number of the person you wished to call |
| When useful | When most or all telephone calls had to be placed by an operator |
Before the widespread adoption of electromechanical and later electronic switching of telephone calls, all calls were completed by an operator in your local central office (CO) who would connect your call to an appropriate outbound trunk using a patch cord and plug bay. If the call required connections through multiple central offices, manual intervention was needed at each office to finally complete the call. The operator would then ring the phones at both ends to let parties at both ends know when the call was fully patched. In the case of long distance or international calls, call setup times could be several hours.
This system started to be phased out in the 1960s with the introduction of electromechanical relays in the central office that would automatically route the calls based on the number that was dialed, however as these systems had many complex moving parts, they required constant maintenance. By the 1980s electronic signaling and switching was becoming increasingly common. The process of setting a call up by allocating resources on each segment of the path between two parties is still in use today, however modern switching systems allow a call to be set up within a matter of seconds in most cases.