Editing AC power plugs and sockets (section)

== Unusual types ==
{{For|obsolete types|History of AC power plugs and sockets#Obsolete types}}

=== Lampholder plug ===
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File:Lampholder plugs.jpg|Italian bypass lampholder plugs with Edison screw mount.<br />Left: early type (porcelain and brass, c. 1930).<br />Right: late type (black plastic, c. 1970)
File:Lampholder plug adapter.jpg|Lampholder plug (US, c. 1950–1960)
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A lampholder plug fits into a light socket in place of a [[Electric light|light bulb]] to connect appliances to lighting circuits. Where a lower rate was applied to electric power used for lighting circuits, lampholder plugs enabled the consumers to reduce their electricity costs.<ref>{{cite web |url=https://www.worldstandards.eu/electricity/history/why-no-universal-plug/ |title=Why isn't there a universal standard electric plug? |website=WorldStandards.eu |access-date=13 December 2024}}</ref> Lampholder plugs are rarely fused. Edison screw lampholder adaptors (for NEMA&nbsp;1-15 plugs) are still commonly used in the Americas.
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=== Soviet standard GOST 7396 C&nbsp;1 unearthed ===
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File:Soviet Plug Type1 6A 250V.jpg|Soviet grip plug, 6&nbsp;A 250&nbsp;V AC, thermoset plastic
File:Soviet Plug Type2 6A 250V.jpg|Soviet round plug, 6&nbsp;A 250&nbsp;V AC, thermoset plastic, half height
File:Soviet moulded rubber plugs 6A 250V cut.jpg|Moulded rubber Soviet plugs cut with knife so that they can fit into CEE&nbsp;7/3 socket. Originally the plugs had a round base.
File:Soviet shaver power cord.jpg|Soviet shaver power cord. The plug is similar to CEE&nbsp;7/16, but has different configuration. Thermoplastic plug is rated 6&nbsp;A and 250&nbsp;V.
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{{further|GOST 7396#Group C}}

This Soviet plug, now rarely used, has pin dimensions and spacing equal to the Europlug, but lacks the insulation sleeves. Unlike the Europlug, it is rated 6&nbsp;A. It has a round body like the European CEE&nbsp;7/2 or flat body with a round base like CEE&nbsp;7/17. The round base has no notches. The pins are parallel and do not converge. The body is made of fire-resistant [[Thermosetting polymer|thermoset plastic]]. The corresponding 6&nbsp;A socket accepts the Europlug, but not others as the 4.5&nbsp;mm holes are too small to accept the 4.8&nbsp;mm pins of CEE&nbsp;7/4, CEE&nbsp;7/6 or CEE&nbsp;7/7 plugs.

There were also moulded rubber plugs available for devices up to 16&nbsp;A similar to CEE&nbsp;7/17, but with a round base without any notches. They could be altered to fit a CEE&nbsp;7/5 or CEE&nbsp;7/3 socket by cutting notches with a sharp knife.
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=== Soviet adaptor plugs ===
[[File:Soviet power plug.JPG|thumb|Soviet adaptor plug]]

Some appliances sold in the Soviet Union had a flat unearthed plug with an additional pass-through socket on the top, allowing a stacked arrangement of plugs. The usual Soviet apartment of the 1960s had very few sockets, so this design was very useful, but somewhat unsafe; the brass cylinders of the secondary socket were uncovered at the ends (to allow them to be unscrewed easily), recessed by only 3&nbsp;mm, and provided bad contact because they relied on the secondary plug's bisected expanding pins. The pins of the secondary plug (which lacked insulation sleeves) could not be inserted into the cylindrical sockets completely, leaving a 5&nbsp;mm gap between the primary and secondary plugs. The adaptors were mostly used for low power appliances (for example, connecting both a table lamp and a radio to a socket).

{{anchor|Walsall|walsall}}

=== UK Walsall Gauge plug ===
[[File:WG13 PICT6943.jpg|thumb|upright=0.85|Walsall Gauge 13&nbsp;A plug (bottom) compared to regular BS&nbsp;1363 plug]]

Unlike the standard BS&nbsp;1363 plugs found in the UK, the earth pin is on a horizontal axis and the live and neutral pins on a vertical axis. This style of plug/socket was used by university laboratories (from batteries) and the [[BBC]], and is still in use in parts of the [[London Underground]] for 110&nbsp;V{{spaces}}AC voltage supply.<ref>{{cite web |url=http://www.plugsocketmuseum.nl/British2.html |title=Non-standard BS 1363 types |work=Museum of Plugs and Sockets |access-date=3 November 2019}}</ref> In the 1960s they were used for 240&nbsp;V&nbsp;DC in the Power laboratory of the Electrical Engineering department of what was then [[Cardiff University|University College, Cardiff]]. Power was supplied by the public 240&nbsp;V&nbsp;DC mains which remained available in addition to the 240&nbsp;V&nbsp;AC mains until circa 1969, and thereafter from in-house rectifiers. They were also used in the [[Ministry of Defence Main Building]] inside circuits powered from the standby generators to stop staff from plugging in unauthorized devices. They were also known to be used in some [[British Rail]] offices for the same reason.
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=== Italian BTicino brand Magic Security connector ===
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File:Bticino Magic 1.jpg|Magic Security socket, detail.
File:Bticino Magic 2.jpg|Assortment of Magic Security sockets (in orange, the industrial three-phase type)
File:Bticino Magic 3.jpg|Assortment of Magic Security plugs
File:Spina magic 02.jpg|Magic Security plug (10&nbsp;A) (left) with a type L to Magic Security plug adaptor
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In the 1960s, the Italian firm [[Bticino|BTicino]] introduced an alternative to the Europlug or CEI&nbsp;23-16 connectors then in use, called Magic Security.{{sfn|De Cesco|1975|p=73}} The socket is rectangular, with lateral key pins and indentations to maintain polarisation, and to prevent insertion of a plug with different current ratings. Three single-phase general purpose connectors were rated 10&nbsp;A, 16&nbsp;A and 20&nbsp;A; and a three-phase industrial connector rated 10&nbsp;A; all of them have different key-pin positioning so plugs and sockets cannot be mismatched.{{sfn|De Cesco|1975|p=75}} The socket is closed by a safety lid (bearing the word ''Magic'' on it) which can be opened only with an even pressure on its surface, thus preventing the insertion of objects (except the plug itself) inside the socket. The contacts are positioned on both sides of the plug; the plug is energised only when it is inserted fully into the socket.

The system is not compatible with Italian CEI plugs, nor with Europlugs. Appliances were never sold fitted with these security plugs, and the use of adaptors would defeat the safety features, so the supplied plugs had to be cut off and replaced with the security connector. Even so, the ''Magic'' security system had some success at first because its enhanced safety features appealed to customers; standard connectors of the day were not considered safe enough.{{sfn|De Cesco|1975|p=73}} The decline of the system occurred when safety lids similar to the Magic type were developed<ref>{{cite web |url=http://www.vimar.eu/index.php?l=it&module=articles&class=articles&event=__default&menu_item_id=134&content=20 |title=La ricerca della sicurezza. Il brevetto Sicury |website=www.vimar.eu. |access-date=12 February 2009}}</ref> for standard sockets.

In Italy, the system was never definitively abandoned. Though very rarely seen today, it is still marked as available in BTicino's catalogue,<ref>{{cite web |url=https://bticino.assetbank-server.com/bticino/assetfile/50782.pdf |archive-url=https://web.archive.org/web/20210224161322/https://bticino.assetbank-server.com/bticino/assetfile/50782.pdf |url-status=dead |archive-date=24 February 2021 |website=bticino.assetbank-server.com |title=Il Classico Dell'Installazione Civile |access-date=20 May 2017}}</ref> (except for the three-phase version, which stopped being produced in July 2011).

In Chile, 10&nbsp;A Magic connectors are commonly used for computer/laboratory power networks, as well as for communications or data equipment. This allows delicate electronics equipment to be connected to an independent circuit breaker, usually including a [[surge protector]] or an [[uninterruptible power supply]] backup. The different style of plug makes it more difficult for office workers to connect computer equipment to a standard unprotected power line, or to overload the UPS by connecting other office appliances.

In Iceland, Magic plugs were widely used in homes and businesses alongside Europlug and Schuko installations. Their installation in new homes was still quite common even in the late 1980s.