Museum of Plugs and Sockets logo, small Schuko Garage socket
locking connected plugs
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plugs
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plugs
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Already before a 1910 VDE* regulation prohibited that a plug under tension could be withdrawn from a socket. The rule applied to voltages above 250V. Removing a plug under tension may cause spark formation between pin and contact, which is dangerous in environments with a risk of explosions due to flammable gases (garage) or flour dust (grain mills). Three-phase 380 Volt locking systems were bulky and expensive; see Kontakt AG example.

From the 1920s locking sockets systems have been developed also for voltages below 250V. These systems required special types of plugs; see the Mahler & Kaege example.

In the 1930s the 220V Schuko system became the standard, domestic earthed socket and plug in Germany.
For three-phase 380V a new plug was developed according to the same Schutz Kontakt principles (see image 7b).
Switched, locking 220 and 380 Volt sockets were designated Garage sockets. They have been made until the 1970s.

Images 1-5 show a 220V Schuko socket with two-pole switch, made by Busch-Jaeger.
Another, very similar example in the museum collection has a single pole switch (image 6). The socket was designed by Busch-Jaeger for Miele washing machines.

380V examples of comparable locking sockets are not in the museum collection. Instead, images of a 1967 catalog are shown in images 7 and 8.

Garage sockets similar to the Busch-Jaeger model have also been made by other German manufacturers, as ABL, AEG and Siemens.

* Verband Deutscher Elektrotechniker founded in 1893.

       

Busch-Jaeger Garage socket (1)
1 - 4

Bakelite, combined Schuko socket and switch, made by Busch-Jaeger in Schalksmühle (logo top right).

Rating: 10A - 250V. Dating: probably a 1950s model.   {WN}

The knob of the rotary swich is - on purpose - not fully round, but has two coves on opposite sides. The significance is explaned below.
Busch-Jaeger Garage socket (2)
The position of the coves as shown in image 1 allows to lift the socket cover (image 2). The switch is turned off. A plug can be inserted (image 3). Rotating the knob 90° turns the switch on, and locks the plug (image 4).

Removing the plug is only possible with the switch in off position. The cover can be closed. The cover shape makes it impossible to switch the socket on with closed cover.

The locking mechanism is functional only if the plug has a collar (green arrow). Nearly all classic Schuko plugs have a collar.
Busch-Jaeger Garage socket (3)
Busch-Jaeger Garage socket (4)
Busch-Jaeger Garage socket (5a)

5

To connect the wall socket to mains, the Bakelite top part has to be removed. Three pins connect the socket contacts with the porcelain (steatite) base.

The rotary switch has four contacts. The top and bottom views of the steatite base shows the socket wiring. Both line (brown) and neutral (blue) are interrupted by the two-pole switch.

6

A similar socket has been designed for connecting Miele washing machines. The Busch-Jaeger model made for Miele has a single pole switch.
A locking socket for washing machines was useful, because in a laundry room, with a lot of steam, sparks could cause dangerous currents on wet surfaces.
Modern washing machines produce no longer clouds of steam.
Busch-Jaeger Garage socket (5b)
Busch-Jaeger Garage socket (6)

 

Schuko 380V Garage socket
 Schuko 380V plug
Perilex 380V Garage socket
 Perilex 380V plug

7

Garage socket (7a) for classic three-phase 380V - 10A Schuko plugs (7b). The designation 'Schuko' (Schutz Kontakt) refers to both domestic 250V single phase and 380V three-phase plugs and sockets.
They share two safety characteristics: sockets are recessed, and earth clips make contact first (together with neutral clips of 380V plugs).
Also three-phase plugs have a collar (green arrows) to lock switched on plugs.
8

Garage-type sockets have been made also for Busch-Jaeger 380V Perilex plugs (8b). Comparable to Schuko, also Perilex sockets are recessed and the flat earth pin makes contact first (because the socket earth contact has a more advanced position than round pin contacts).
Older Perilex plugs (initially rated at 15A) have a collar (green arrows) to lock switched on plugs.
See pre-IEC 60309 page for additional info re. Perilex.

The museum is grateful to Reiner Hahn for providing information about German Garage sockets, and screenshots taken from a Neumann Elektrotechnik, Düsseldorf 1967 catalog (image 7a and 8a).

 

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