Editing LocalTalk

{{Short description|Implementation of AppleTalk networking}}
{{Use mdy dates|date=October 2013}}
{{More citations needed|date=March 2023}}
{{multiple image
   | footer    = Interior of Apple LocalTalk interface box. In 1989, these boxes typically cost {{Currency|90|USD|linked=no}} ({{Inflation|US|90|1989|fmt=eq|r=-1}}{{Inflation/fn|US}}) each. The connectors feature automatic [[electrical termination]] of the LocalTalk signal bus; insertion of a LocalTalk bus cable depresses a [[normally closed]] [[switch]] behind the connector, disabling termination for that connector.
   | width1     = 155
   | image1    = Apple LocalTalk box interior 1.jpg
   | alt1      = Local cable and interior circuit board, port-side view
   | width2     = 125
   | image2    = Apple LocalTalk box interior 2 - auto termination switch.jpg
   | alt2      = Rear view of auto-termination switch with dust cover removed
  }}
'''LocalTalk''' is a particular implementation of the [[physical layer]] of the [[AppleTalk]] [[Computer networking|networking]] system from [[History of Apple Inc.|Apple Computer]]. 

LocalTalk specifies a system of [[shielded twisted pair]] cabling,<ref>{{Cite web |date=2010-02-02 |title=AppleTalk Overview |url=https://www.cisco.com/c/en/us/td/docs/ios/at/configuration/guide/12_2sx/atk_12_2sx_book/overview_appletalk.pdf |access-date=2023-03-21 |website=[[Cisco]]}}</ref> plugged into self-terminating [[transceiver]]s, running at a rate of 230.4&nbsp;kbit/s. [[Carrier-sense multiple access with collision avoidance|CSMA/CA]] was implemented as a random multiple access method.

[[Image:Farlon localtalk.jpg|thumb|right|Farallon's competing PhoneNet transceiver]]

Networking was envisioned in the [[Mac (computer)|Macintosh]] during planning, so the Mac was given expensive [[RS-422]] capable [[serial port]]s, first on a [[DE-9 connector|nine-pin D-connector]], then on a [[Mini-DIN connector|mini-DIN-8]] connector. The ports were driven by the [[Zilog SCC]], which could serve as either a standard [[Universal asynchronous receiver-transmitter|UART]] or handle the much more complicated [[High-Level Data Link Control|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&nbsp;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&nbsp;MHz clock after the customary divide-by-16. This clock frequency, 3.6864&nbsp;MHz, was chosen (in part) to support the common asynchronous baud rates up to 38.4&nbsp;kbit/s using the SCC's internal baud-rate generator. When the SCC's internal [[phase-locked loop|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&nbsp;kbit/s.

Originally released as "AppleTalk Personal Network", LocalTalk used shielded twisted-pair cable with three-pin [[Mini-DIN connector|mini-DIN]] connectors. Cables were [[daisy chain (electrical engineering)|daisy-chained]] from transceiver to transceiver. Each transceiver had two three-pin mini-DIN ports, and a "pigtail" cable to connect to the Mac's [[DE-9 connector|DE-9]] serial connector. Later, when the [[Macintosh Plus|Mac Plus]] introduced the eight-pin mini-DIN serial connector, transceivers were updated as well.

A variation of LocalTalk called [[PhoneNET]] was introduced by [[Farallon Computing]]. It used standard unshielded side-by-side telephone wire, with six-position [[modular connector]]s (same as the popular [[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.<!-- Is this true? Proper Apple LocalTalk cables were locking also. --> 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 network|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 [[Ethernet]]-based networking in the early 1990s led to the swift disappearance of both LocalTalk and PhoneNET. They remained in use for some time in low-cost applications and applications where Ethernet was not used. [[Macintosh Quadra]] and early models of [[Power Macintosh]] supported both [[10BASE2]] and [[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 [[PowerBook]]s.{{Citation needed|date=January 2011}} 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&mdash;and thus, the ability to use both LocalTalk and PhoneNET&mdash;disappeared from new models of Macintosh. [[LocalTalk-to-Ethernet bridge]]s were introduced to allow [[legacy system|legacy devices]] (especially [[printer (computing)|printer]]s) 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#Physical_implementation|AppleTalk Connector Family]] design, created by [[Brad Bissell]] of [[Frog Design]] using [[Rick Meadows]]' [[Apple Icon Family]] designs.{{Citation needed|date=March 2008}}<!-- Unable to find evidence of either term via Google, and Frogdesign no longer appears to list Apple as a client... --> LocalTalk connectors were first released in January 1985 to connect the [[LaserWriter]] printer initially with the [[Mac (computer)|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|date=January 2011}}

==References==
{{Reflist}}

==See also==
{{Commons category|LocalTalk}}
* [[AppleTalk]]
* [[Econet]]
* [[List of device bandwidths]]

{{Apple hardware before 1998}}
{{Apple hardware}}

{{DEFAULTSORT:Localtalk}}
[[Category:Apple Inc. hardware]]
[[Category:Computer network technology]]
[[Category:Network protocols]]
[[Category:Networking hardware]]
[[Category:Physical layer protocols]]
[[Category:Link protocols]]
[[Category:Legacy hardware]]