Museum of Plugs and Sockets logo, small Classic continental European
not earthed multi-plugs and adapters
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Images 1 -14 show multi-plugs, also known as connector plugs. They are plugs with 1, 2, 3 or 4 outlets. In case of only one outlet there is also a possibility to connect the cord of an appliance.

Multi-plugs were popular from the early days of home electrification, because a room often had not more than a single socket.
Classic examples shown are not earthed. Although earthed sockets and plugs existed already in the 1910s, they were uncommon for domestic use until the mid 1930s.
Note that the shown multi-plugs are regarded as unsafe and from the 1980s- '90s (country dependent) it is not allowed anymore to produce and sell them.

Unless stated otherwise, plugs and matching outlets have the following characteristics in common:
1. Pin diameter of 4 mm and pin spacing of 19 mm. Outlets are designed for the same type of plugs
2. Rating, if indicated, of 6 Amp - 250 Volt. Rating refers to the total load.


Ebonite 2-way milti-plug Ebonite 2-way multi-plug
Ebonite 4-way multi-plug
Ebonite 3-way multi-plug

Steatite 2-way multi-plug
Steatite 2-way multi-plug
Porcelain multi-plug made by Oger
Multi-plug made by Domino

1 Very early 2-way multi-plug, made of an early synthetic press material, possibly ebonite.  Manufacturer: AEG (Allgemeine Elektrizitätsgesellschaft) in Berlin. The shown model 1168 is listed in a 1911 AEG catalog.   {RH}
2 Ebonite 2-way multi-plug. Origin is unknown. Dating: 1920s.
3 Ebonite 4-way multi-plug. Unknown origin. Dating: late 1920s*. Plugs with 19 mm pin spacing can only be inserted in horizontal position. Note the difference in coloring compared to plug nos. 2 and 4. Ebonite is deeply black when new. Over decades it becomes brown and may look like old timber.
* a 1929 catalog of Hans F. Wilke, wholesaler in Hamburg shows a comparable Hartgummi Vierfachstecker.
4 3-way multi-plug made of ebonite are comparable press material. Unknown origin; probably late 1920s.   {RH}
5, 6
Two examples of black glazed steatite 2-way multi-plugs. Unknown origin; probably 1920s.   {RH}
7 Porcelain plug with a single outlet. The two small holes (spacing 16 mm), visible on the image bottom right, are wire entries. It is an 1920s, or earlier model, made by Felix Hofmann in Berlin-Charlottenburg. He used the trademark Oger.   {RH}
8 French plug with single outlet and cable connection. Manufacturer is unknown. Probably made of a Bakelite-like pressed material.   {WN}

The plug carries two inscriptions: (i) BTE SGDG
which means that the plug is guaranteed by the manufacturer, but this guarantee is not recognized by the government (Breveté Sans Garantie Du Gouvernement")* and (ii) DOMINO.
Domino refers to a method of stacking multiple plugs as nos. 7 and 8. The image right has been copied from a 1933 catalog of Bouchery, wholesaler in Paris. It will be clear that a socket with multiple outlets offers a much more safe method to connect five appliances (see no. 16). The only safe place for an Oger or Domino plug is a museum.

* In France it was until 1968 a common way of indicating a patent. Testing of functionality, safety etc. by the manufacturer was not compulsory and a warranty that the manufacturer will repair or replace the article in case of a fault was not included.
Stack of multi-plugs
  Image provided by Reiner Hahn

Steatite multi-plug made by Brunnquell Bakelite multi-plug made by WISI Three examples of Bakelite multi-plugs

3-way multi-plug made of timber Multi-plug for not eathed plug but fit in Schuko socket
White resin 3-way multi-plug

9 Steatite 3-way multi-plug, made by Brunnquell & Co., Fabrik elektrotechnische Apparate und Beleuchtungen in Sondershausen (Thüringen). Dating: 1920s. The Brunnquell company was founded in 1913. Shortly after the end of WW II the company was expropriated and finally incorporated in VEB* Elektroinstallation Sondershausen (EIS).
* VEB stands for Volkseigener Betrieb, the main - publicly owned - legal from of industrial enterprises in the former German Democratic Republic (DDR).
10 Bakelite 3-way multi-plug made by Wilhelm Sihn in Niefern (Baden). Dating of product no. 56: late 1930s.
The company was founded in 1926 and still exists as WISI Group, now specialized in receiving and distribution technology.  
11 Three examples of Bakelite 3-way multi-plugs that were produced in large quantities and used during many decades. Approximate dating: (a) from mid 1930s; (b) from early 1950s; (c) 1960s. Manufacturers: (a) Elektro-Praga; (b,c) not indicated.   {WN}
12 Timber 3-way multi-plug. For a short period during mid 1940s wood was used for plugs, because of shortage of more appropriate materials.   {WN}
13 The shape of the basal part of this 3-way multi-plug has two grooves (green arrows). Pins have a diameter of 5.0 rather than 4.0 mm. The plug was designed for fitting in Schuko (CEE 7/3) sockets, but the outlets are meant for not earthed plugs with 4.0 or 4.8 mm pins. To emphasize the lack of earth contacts, despite being plugged in an earthed socket, the top outlet has a clear warning: VORSICHT NICHT GEERDET (caution not earthed). Unknown origin. Dating: 1970s or earlier.   {WN}
14 3-way multi-plug that only can be used safely with a flex cord connector or a fully flat sockets that were available in Italy and Switzerland. It can't be used in any recessed socket, because of the rectangular basis size (42x34 mm).  3.9 mm pins are only 16 mm long. Unknown origin. Dating: 1960s - '70s?   {WN}

Siemens porcelain Anschlusswuerfel Inventum 5-way outlet

15 Flex cord with porcelain, quadruple outlet, made by Siemens-Schuckertwerke in Berlin. A 1929 Siemens catalog mentions that the Anschlusswürfel mit 4 Steckflächen was available in three variants: (1) only the porcelain cube, (2) cube with 2 meter flex cord and plug, and (3) cube with cord and "Zeta-Pendeldose". The last was a special ceiling socket that consisted of a part fixed to ceiling and an interchangeable part connected to the flex cord of a lamp or cube*. See image below (source, p.48). When using the cube in the early morning or evening you need an additional table lamp (see photo of breakfast table).   {RH}

* modern lamp sockets and plugs offer a comparable possibility to switch between light and power.

Siemens Zeta-Pendeldosen


breakfast table
with cube outlet
Siemens advertisement with dining table

16 Power strip that can accommodate five plugs. This robust ebonite multi-outlet is fixed on a wooden base. A comparable multi-outlet extension cord can be seen on a photo in the 1918 catalog of the Dutch company Inventum (see advertisement on appliance couplers overview page). The five-fold outlet shown here date probably back to the mid 1930s.

Felmas 6-way hexagonal outlet Felmas 6-way hexagonal outlet, details

17, 18
Hexagonal, Bakelite six-fold outlet, made by Gustav Schortmann & Sohn, Fabrik elektrotechnischer Spezial-artikel in Leipzig, who used the trademark FELMAS. Indicated rating: 6 x 1.5A - 250V. Schortmann did not had its own Bakelite pressing facility; MPAD marks  show - upside down - that press work was contracted out to Bisterfeld und Stolting in Radevormwald (close to Wuppertal). Dating: mid 1930s    {WN}

adapter with 4 mm pins for Schuko plugs adapter with E27 fitting
Diazes fuse box with adapter

Kirsammer tap-on plug
Austrian 2A tap-on plug
Austrian 2A tap-on plug, details

19 Adapter making sockets for 4.0 mm plugs accessible to 4.8 mm plugs.
20 Porcelain adapter with 27 mm Edison screw base fitting to single 2-pin outlet. It may date back to the 1910s. In those days home electricity was almost exclusively used for illumination. Wall sockets were very rare. Table lamps and electric implements had to be connected by lamp holder adapters (see also no. 33).
Later, when separate sockets were commonly installed - initially one per room - it could still be profitable to use lamp adapters, because there were often different tariffs for electricity used for lighting, domestic appliances and commercial use (see classic uncommon page for details). For that reason, they were also known as current thiefs. However stealing was not always profitable because some electricity providers had an higher tariff for lighting. Next image shows a different application.   {PM}
21 Lamp adapters have also been used for inspection of domestic electrical circuits. In Germany, and several other continental European countries, D-type (diazed) fuses were commonly used in main fuse boxes. D-fuse cartridges are secured with 27 mm Edison screw caps. Temporarily, a fuse can be replaced by an E27 screw base lamp adapter. For inspection purposes a current meter can be coupled to the adapter outlet. Information about the use of the adapter has been given by Peter Martin.
22 Combined plug for connection of an appliance or flex cord and a single outlet for another not earthed plug with 4 mm pins. Cast has been made by W. Kirsammer, Kunstharzpresserei in Plochingen near Stuttgart (MPAD code UW), but the plug manufacturer seems to be a yet unknown company that had a logo with capitals RRS. Dating: late 1950s.   {WN}
23, 24
Combined plug and outlet rated at 2A - 250V. The design has been patented in 1955 (Austrian Patent nr. 185.863). Patent was granted to Heinrich Ulbricht's Wwe* GmbH in Schwanenstadt, Austria; hence the WweU logo. (*Wwe = Witwe, widow).  {CW}

Thega-Kontakt multi plug
Thega-Kontakt multi-plug with shutters Thega-Kontakt multi-plug with shutters AEG 3-way multi-plug

↓ ↑
AEG 3-way multi-plug
AEG 3-way multi-plug
AEG 3-way multi-plug
AEG 3-way multi-plug

25 Bakelite 2-way multi-plug, rated at 6A-250V made by Thega-Kontakt in Berlin. A list of Jewish businesses in Berlin shows that Thega-Kontakt was founded in 1923 and confiscated by Nazi German authorities in 1938.   {PM}
26, 27 Bakelite 3-way multi-plug rated at 6A - 250V, made by Thega-Kontakt. The multi-plug has safety shutters on each of the three outlets (see enlargement in image no. 27). To tip over the shutters, both pins of a plug has to be inserted simultaneously. Patent has been filed or issued, but a patent number is not indicated.
In Germany safely shutters were uncommon in the 1930s. It could be that they were introduced by Thega-Kontakt.   {PM}
28, 32
Multi-plug for three not earthed plugs with 4.0 mm pins, rated at 6A - 250V.It has a remarkable safety feature, see image nos 29-31 and caption below. It has a hexagonal type AEG logo that was designed by Peter Behrens in 1908. The original design showed the capitals A, E and G in the three smaller hexagons. The Bakelite multi-plug has been made from the 1930s until 1950s. A very similar model has also been made by Felmas (Leipzig) in the 1930s (source: Reiner Hahn).   {RH}
29 - 31 For many multi-plugs shown on this page it is possible to fully insert a plug with one pin only. If the plug is attached to appliance, there is a substantial chance that the other, unprotected pin is under tension.
The AEG multi-plug has one recessed outlet that makes it impossible to fully insert just one pin (see image no. 29). The partly inserted pin does touch the multi-plug contact. When a round plugs is inserted correctly (image no. 30) pins can't be touched because of the recess; another safety feature that is rather uncommon for not earthed multi-plugs. The wide circular plateaus around the other two outlets have the same function; a single pin can not touch the contact (image no. 31).

He-Ku socket
He-Ku socket
He-Ku socket

Classic porcelain lamphoder with 2 two outlets
Classic Bakelite lamphoder with 2 two outlets

33 - 35 Not earthed socket with outlets on opposite sides. Rating: 6A - 250V. Contacts 1 and 3 (image 34) correspond to one side of the sockets, contacts 2 and 4 to the opposite side. The two modern flat plugs (image 35) make clear that plugs are 42° rotated with respect to each other because of connection to respectively contacts 1-3 and 2-4. Socket size: 56 x 45 mm; 23 mm thick.
The socket has three marks: He Ku (unknown manufacturer), No 81 (model), and DRGM (Deutsches Reich Gebrauchsmuster, a German patent-like intellectual property right, used from 1891 until 1945.   {WN}
36, 37
Two examples of adapters with a 27 mm Edison screw base and two not earthed outlets for plugs with 4.0 mm pins. Identical with respect to functionality, but design and dating are different. No. 36 is made of porcelain and dates back the 1920s. Bakelite adapters have made from the 1930s to 1960s. No. 36 carries initials SKB (unknown company). No. 37 has been made by Bender & Wirth in Kierspe (Westfalen). Dating: late 1950s - early 1960s.   {WN}


Image from 1959 VDE leaflet

Image taken from leaflet no. 0100 issued by German VDE in November 1958.

The use of devices, also with recessed outlets, in combination with screw cap fittings is prohibited (image 37)

Wall sockets have to be mounted at least 30 cm above floor level.

Image 37
Examples of prohibited devices

Multi-plugs, also with recessed outlets and protective earth contact (image 37), are permitted only until 31 October 1959.

Note that the shown devices and similar plugs and adapters are banned not only in Germany but later also in several other European countries.
However, in the Netherlands recessed, Schuko and/or Europlug multi-plugs are still [2016] allowed.


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