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  2. British telephone socket - Wikipedia

    en.wikipedia.org/wiki/British_telephone_socket

    Plug-in extension kits are available for customers with this type of installation. The two wires from the exchange are denoted the B leg at −48 V relative to ground when the line is not in use and the A leg which is near ground potential when the line is not in use. The A leg goes to pin 5 and the B leg to pin 2 in the master socket ...

  3. List of telephone switches - Wikipedia

    en.wikipedia.org/wiki/List_of_telephone_switches

    Connection was made via a crossbar switch. A SP1 2-wire variant was also available that provided Centrex services. A version of the SP-1 ESS that could provide both 2 & 4 wire services was also built. The first instance was installed in Vegreville Alberta in 1976 or 1977. SP1 4-Wire (Toll)

  4. SP-1 switch - Wikipedia

    en.wikipedia.org/wiki/SP-1_switch

    A "two wire" version for local service, a four wire version for toll service. Two/four wire versions were also available as was a TOPS variant that was used to provide Operator services. The first four wire switch (four wire-tops, i.e., it provided toll switching and operator services) was placed in service in Thunder Bay circa 1972.

  5. Punch down tool - Wikipedia

    en.wikipedia.org/wiki/Punch_down_tool

    A punch down tool, punchdown tool, IDC tool, or a Krone tool (named after the Krone LSA-PLUS connector), is a small hand tool used by telecommunication and network technicians. It is used for inserting wire into insulation-displacement connectors on punch down blocks , patch panels , keystone modules , and surface mount boxes (also known as ...

  6. Multiway switching - Wikipedia

    en.wikipedia.org/wiki/Multiway_switching

    In building wiring, multiway switching is the interconnection of two or more electrical switches to control an electrical load from more than one location.A common application is in lighting, where it allows the control of lamps from multiple locations, for example in a hallway, stairwell, or large room.

  7. Number One Electronic Switching System - Wikipedia

    en.wikipedia.org/wiki/Number_One_Electronic...

    The 1AESS central office switch was a plug compatible, higher capacity upgrade from 1ESS with a faster 1A processor that incorporated the existing instruction set for programming compatibility, and used smaller remreed switches, fewer relays, and featured disk storage. [2] It was in service from 1976 to 2017.

  8. Knob-and-tube wiring - Wikipedia

    en.wikipedia.org/wiki/Knob-and-tube_wiring

    The conduit methods were known to be of better quality, but cost significantly more than K&T. [2] In 1909, flexible armored cable cost about twice as much as K&T, and conduit cost about three times the price of K&T. [6] Knob and tube wiring persisted since it allowed owners to wire a building for electricity at lower cost.

  9. Twist-on wire connector - Wikipedia

    en.wikipedia.org/wiki/Twist-on_wire_connector

    Twist-on wire connectors are not generally recommended for use with aluminum wire in the United States. [1] The U.S. Consumer Product Safety Commission disapproves wire nuts for aluminum wire; instead, special crimp connectors are called for, and as of 2011 the CPSC asserted qualified, second-preference approval of a certain kind of screw ...