In telephony, a switch is a device within a telephone exchange, such as the public switched telephone network (PSTN), that connects calls from the requester to the destination. They're typically found in central offices, which are large switching stations operated by phone service providers. An individual call may travel through several central offices on the way to the call recipient and the hand-offs are all enabled by switches. In addition to processing voice transmissions, switches can also facilitate digital communications by connecting computer modems to whatever location they request.
Switches include both a hardware and a software component. In fact, switching software automated tasks originally carried out by large numbers of human phone switch operators. The software manages the physical connections between incoming calls and the appropriate outgoing circuits. Anyone using landline phones is interacting with this smart technology from the moment they lift the receiver and hear a dial tone.
Telephone switches are part of the backbone of our current telecommunications system.
