LocalTalk

normally closed switch

behind the connector, disabling termination for that connector.

LocalTalk is a particular implementation of the

LocalTalk specifies a system of

shielded twisted pair cabling,^[2] plugged into self-terminating transceivers, running at a rate of 230.4 kbit/s. CSMA/CA

was implemented as a random multiple access method.

Networking was envisioned in the

nine-pin D-connector, then on a mini-DIN-8 connector. The ports were driven by the Zilog SCC, which could serve as either a standard UART or handle the much more complicated HDLC

protocol, which was a packet oriented protocol that incorporated addressing, bit-stuffing, and packet checksumming in hardware. Coupled together with the RS422 electrical connections, this provided a reasonably-high-speed data connection.

The 230.4 kbit/s bit rate is the highest in the series of standard serial bit rates (110, 150, 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200, 230400) derived from the 3.6864 MHz clock after the customary divide-by-16. This clock frequency, 3.6864 MHz, was chosen (in part) to support the common asynchronous baud rates up to 38.4 kbit/s using the SCC's internal baud-rate generator. When the SCC's internal PLL was used to lock to the clock embedded in the LocalTalk serial data stream (using its FM0 encoding method) a divide-by-16 setting on the PLL yielded the fastest rate available, namely 230.4 kbit/s.

Originally released as "AppleTalk Personal Network", LocalTalk used shielded twisted-pair cable with three-pin

DE-9 serial connector. Later, when the Mac Plus

introduced the eight-pin mini-DIN serial connector, transceivers were updated as well.

A variation of LocalTalk called

RJ11 telephone connectors) connected to a PhoneNET transceiver, instead of the expensive, shielded, twisted-pair cable. In addition to being lower cost, PhoneNET-wired networks were more reliable due to the connections being more difficult to accidentally disconnect. In addition, because it used the "outer" pair of the modular connector, it could travel on many pre-existing phone cables and jacks where just the inner pair was in use for RJ11 telephone service. PhoneNET was also able to use an office's existing phone wire, allowing for entire floors of computers to be easily networked. Farallon introduced a 12-port hub, which made constructing star topology

networks of up to 48 devices as easy as adding jacks at the workstations and some jumpers in the phone closet. These factors led to PhoneNET largely supplanting LocalTalk wiring in low-cost networking.

The useful life of PhoneNET was extended with the introduction of LocalTalk switching technology by Tribe Computer Works. Introduced in 1990, the Tribe LocalSwitch was a 16-port packet switch designed to speed up overloaded PhoneNET networks.

The widespread availability of

10BASE-T via the Apple Attachment Unit Interface (AAUI), and all other Ethernet media via an AAUI–AUI adapter, while still supporting LocalTalk-based networking. For older Macintosh computers that did not have built-in Ethernet, a high-speed SCSI-to-Ethernet adapter was available, and was particularly popular on PowerBooks.^{[citation needed}

] This enabled all but the earliest Macintosh models to access a high-speed Ethernet network.

With the release of the iMac in 1998 the traditional Mac serial port—and thus, the ability to use both LocalTalk and PhoneNET—disappeared from new models of Macintosh. LocalTalk-to-Ethernet bridges were introduced to allow legacy devices (especially printers) to function on newer networks. For very old Macintosh computers, LocalTalk remains the only option.

Design legacy

The LocalTalk connector had the distinction of being the first to use Apple's unified AppleTalk Connector Family design, created by Brad Bissell of Frog Design using Rick Meadows' Apple Icon Family designs.^{[citation needed]} LocalTalk connectors were first released in January 1985 to connect the LaserWriter printer initially with the Macintosh family of computers as an integral part of the newly announced Macintosh Office. However, well past the move to Ethernet, the connector's design continued to be used on all of Apple's peripherals and cable connectors as well as influencing the connectors used throughout the industry as a whole.^{[citation needed]}

References

^ 1634–1699: McCusker, J. J. (1997). How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States: Addenda et Corrigenda (PDF). American Antiquarian Society. 1700–1799: McCusker, J. J. (1992). How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States (PDF). American Antiquarian Society. 1800–present: Federal Reserve Bank of Minneapolis. "Consumer Price Index (estimate) 1800–". Retrieved February 29, 2024.
^ "AppleTalk Overview" (PDF). Cisco. February 2, 2010. Retrieved March 21, 2023.

Design legacy

References

See also