LocalTalk is a system of shielded twisted-pair cabling with 3-pin Mini-Deutsches Institut für Normung (Mini-DIN) connectors. The cabling plugs into self-terminating transceivers and operates at a data transmission rate of 230.4 kbps. Originally released as "AppleTalk Personal Network," LocalTalk is one implementation of the physical layer of the Apple Computer networking system known as AppleTalk.

Multi-mode (RS-232/RS-422) capable serial ports, driven by the Zilog Serial Communications Controller (SCC), were given to Macintosh computers in anticipation of possible computer networking.

A high-speed data connection was achieved by the use of the RS-422 electrical connections and the Zilog SCC, since it is able to serve as either a standard Universal asynchronous receiver/transmitter (UART) or as a High-Level Data Link Control (HDLC) protocol, which is a significantly more complicated, packet-oriented protocol that incorporates addressing, bit-stuffing and packet checksumming in hardware.

In LocalTalk, the shielded twisted-pair cables are daisy-chained from transceiver to transceiver using the two 3-pin Mini-DIN ports in each transceiver. Transceivers connected to the Macintosh DE-9 serial connector using a cable. With the introduction of the 8-pin Mini-DIN serial connector in the Mac Plus, transceivers also underwent an update.

Another computer company, Farallon Computing (now known as Netopia), developed PhoneNet, another implementation of the AppleTalk physical layer that made use of standard unshielded twisted-pair telephone wire with 6 position modular connectors (same as used in the popular RJ11 telephone connectors) connected to a PhoneNet transceiver, as a cheaper alternative to shielded twisted-pair cable, which is significantly more costly.

PhoneNet-wired networks were more favorable in comparison to LocalTalk-wired networks since networks using PhoneNet were both less expensive and more reliable, since the connections in a PhoneNet-wired network do not accidentally disconnect as easily. PhoneNet is capable of travel on many pre-existing phone cables and phone jacks where just the inner pair was utilized for RJ-11 telephone service, since PhoneNet made use of the "outer" pair of the modular connector.

Through PhoneNet, entire floors of computers achieved easy networking due to the ability of PhoneNet to make use of an existing phone wire in an office. Construction of star topology networks of up to 48 devices was made easy with the introduction of a 12-port hub by Farallon Computing.

To create such a network, all that needed to be done was add jacks at the work stations and add jumpers in the phone closet. With all of the advantages of PhoneNet over LocalTalk wiring, it became the more commonly-used system in low-cost networking.

Both LocalTalk and PhoneNet were superseded in the early 1990’s with the inception of Ethernet-based networking, which became universal on the personal computer and was installed by most offices. In 1998, iMac was released and new Macintosh models no longer featured the traditional Mac serial port, rendering both LocalTalk and PhoneNet obsolete.