Museum of Plugs and Sockets logo, small Czech Republic
overview of types of plugs and sockets
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In the early years of electrification the nowadays Czech Republic and Slovakia were a part of the Austro-Hungarian Empire. From November 1918 until the end of 1992 the countries were united as Czechoslovakia.
In the 1920s and '30 the country belonged to the top five industrialized states in Europe. Industry was concentrated in Bohemia and Moravia, regions that now constitute the Czech Republic.

Current models of Czech plugs and sockets are shown in image nos. 1 - 14. The museum is indebted to Tomáš Drahoňovský and  ABB Elektro Praga in Jablonec nad Nisou for donating items 1 - 14.
A short history of the company is given below.  Classic material is shown in images 15 - 23.


ABB Elektro Praga series Levit socket
ABB Elektro Praga series Tango dual socket
ABB Elektro Praga series Element dual socket
ABB Elektro Praga

ABB Elektro Praga IP54 socket with lid
ABB Elektro Praga 16A socket
ABB Elektro Praga CEE 7/7 plug
ABB Elektro Praga 10-16A plug

Intro Already in 1933 the Czechoslovakian Electrotechnical Association (ESČ) stipulated that from June 1934 earthed sockets must be installed in all new buildings, homes included. Czechoslovakia was probably the first country in which this safety rule was made mandatory for all new wiring installations.
Initially Czechoslovakia opted for the Schuko system, but finally decided to chose for a royalty-free French/Belgian system, characterized by sockets that have an earth pin (now known as CEE 7/5 standard). Soon thereafter Poland has introduced the same system.

CEE 7/5 standard domestic socket, rated at 16A - 250V. Sockets must have a recess (depth: 14.7 mm). Earth pin diameter: 4.8 mm. Socket earth pin makes contact first when a plug is inserted.
Modern Czech sockets have safety shutters, operated by simultaneous entry of line and neutral pin.

Shown is an example of the ABB Elektro-Praga Levit® line.
2, 3
Dual socket with a 32ş rotated top outlet. Image no. 3* illustrates the benefit of a rotated outlet when using plugs with cord side entry.
* image of the Element® line dual socket has been copied from Czech tzb-info site.
Socket with lid, rated at 16A - 250V. The socket has International Protection rating IP 44* which mean that it can be used among others in bathrooms.
* first digit: protection against ingress of solid objects with a diameter larger than 1 mm; second digit: protected against splash water from any direction.
5 CEE 7/6 plug, rated at 16A - 250V. Pin diameter: 4.8 mm.
Elektro-Praga designed in the 1950s a plug to bridge the gap between earthed sockets used in Czechoslovakia (see no. 1) on the one hand and the German Democratic Republic (using Schuko) on the other. This so called joined plug complied with Czechoslovak ČSN ESČ 107 standard. It became a successful export product.
The image shows an essentially identical, but more recent model, that is now better known as a CEE 7/7 hybrid plug. Rating: 16A - 250V. It will be clear that also not earthed 2.5A CEE 7/16 (Europlug) and 16A CEE 7/17 plugs fit in standard Czech sockets.
7 An example of 10-16A plug with 4.8 mm pins and cord side entry. The plug has a special feature that is shown in the image below.

Czech CEE 7/6 plug no. 5536

Plug no. 7 consists of two parts: (a) thermo-plastic cast, and (b) black body with pins, earth contact and screws for wire attachment. Figs. a+b show the most common method of plug assembling, resulting in plug c (identical to no. 7).
However, mounting the body upside down in cast 'a' is also possible. Next you have to rotate the plug 180ş (see fig. d), because the socket earth pin is always on top. The result of the upside down mounting procedure is that the cord leaves the plug from the top. That could be the preferred option to power a lamp or clock fixed above the socket. A versatile design.

9 - 14
Czechoslovakia had, and both the Czech Republic and Slovakia still have, a variety of uncommon flat pin* plugs and sockets for special purposes. The six types shown below probably date back to the 1930s.
The original Czechoslovak standard ČSN ESČ 153 has been replaced by the Czech standard ČSN 35 4517.
* flat pin size: 5.0 x 2.5 mm, 18.5 mm long. Diameter of round pin (type K): 6.0 mm.
Each of the six types is rated at 10A - 250V (C, C1, C2) / 440V (D) / 48V (K, L). Specifications of intended AC or DC voltage are given in the images below. Low voltage type K is still used in specific industrial environments where 230 Volt is not allowed for safety reasons. The 48V 3-phase type L is occasionally used in energy storage devices.

CSN 35 4517 type C socket and plug
CSN 35 4517 type C pin configuration

Type C

220 V DC

1-pole +E
CSN 35 4517 type C1 socket and plug
CSN 35 4517 type C1 pin configuration

Type C1

110V AC

1-pole +E

CSN 35 4517 type C2 socket and plug
CSN 35 4517 type C2 pin configuration

Type C2

110 V DC

1-pole +E

CSN 354517 type D socket and plug
CSN 35 4517 type D pin configuration

Type D

400 V AC

+N, +E

CSN 35 4517 type K socket and plug
CSN 35 4517 type K pin configuration

Type K

48 V

O = pin
without wire

CSN 35 4517 type L socket and plug
CSN 35 4517 type N pin configuration

Type L

48 V AC


Comparison of pin postitions of CSN 354517 type C and HNA plugs

ČSN 35 4517 lookalike material once made by other companies.

HNA (Handelsschiff-Normen-Ausschuss), a German shipbuilding standard that dates back to the 1920s is similar to type C. However, because of small differences between type C and HNA - see figure left -  the two types are incompatible; even applying force doesn't help.

Stotz-Kontakt model 14219 (see 1939 catalog) is fully identical to type C1.
The German company (now part of ABB Busch-Jaeger) has ended production of the model.

A 4-pin model made by the Austrian company ELIN has a pin configuration that looks similar to type D; see scheme i in a 1936 catalog.


Classic material

Czechoslovak, 6A not earthed plug Czechoslovak 16A earthed plug Polish 10A not earthed plug
Czechoslovak, 10A earthed appliance connector
Czechoslovak 3-way multi-plug, earthed
Czechoslovak 3-way multi-plug, not earthed

15 Bakelite, not earthed plug, rated at 6A-250V. Pin diameter: 4.0 mm. The type of plug does not fit in sockets installed from 1934. Therefore it must have been made for replacement in pre-1934 wiring installations, or it was meant for export.
Manufacturer: Elektro-Praga, artno. 1372. Dating: 1950s.
Earthed, 6A-250V plug suitable for sockets with earth pin. The Czechoslovak standard ČSN ESČ 107 (similar to CEE 7/5-6) became compulsory in 1934. Pin diameter: 4.0 mm; earth contact accepts 4.8 mm pins.
Manufacturer: Elektro-Praga. Dating: 1960s-'70s.   {RH}
17 Not earthed plug, moulded to a flex cord. It is rated at 10A-250V and has 4.0 mm pins. The hole to accommodate the socket earth pin does not have an earth contact. The plug has a Polish, 'B' certification mark. Similar not earthed plugs have also been used and made in Czechoslovakia. Manufacturer and dating are unknown.   {WM}
Earthed appliance connector, similar to German standard DIN VDE 49491, rated at 10A-250V. Connector has a Czechoslovakian ESČ certification mark that is also shown on plug no. 15 and multi-plug no. 19. Dating: 1950s-'60s. Manufacturer: Elektro-Praga, 1052.   {RH}
19 Earthed 3-way multi-plug, rated at 10A-250V. Both power pins and earth pins have a diameter of 4.8 mm. Dating: 1950s-'60s. Manufacturer: Elektro-Praga.   {RH}
20 Not earthed 3-way multi-plug. rated at 6A-250V. Contacts can accommodate plugs with 4.0 mm pins only. The shown model has been made for export and has no certification mark. Manufacturer: Elektro-Praga. Dating: 1950s-'60s.


Logos of Kramer & Loebl, Elektro Praga and ABB

a. Logo used by Kramer and Löbl on electrical accessories (until 1940).

b. Logo introduced in 1946 for the group of manufacturers of electro-technical appliances.

c. Logo on plugs, sockets, switches etc., made in Jablonec nad Nisou from late 1940s.
Found on nos. 6, 15, 16, 18, 19 and 20.

d. Asea Brown Boveri logo on products made from 1993.
Found on nos. 1, 2, 4, 5 and 9 - 14.

Plug no. 7 has both logo 'c' and 'd'.

Plugs made by Kramer and Löbl in the 1930s are missing in the museum collection.
Suggestions were to find them are welcome.

Short history of ABB Elektro Praga                                                               Source

Gustav Kramer and Adalbert Löbl started production of refined glass and crystal lamps and chandeliers in Jablonec nad Nisou (Gablonz in Austro-Hungarian Empire).

With the growth of electrification Kramer and Löbl started production of accessories related to electric lighting, as sockets, plugs and switches. It proved to be a profitable market. Glass production was scaled down and ended in 1924. The company was renamed 'Kramer und Löbl, Fabrik elektrotechnischer Artikel'. Adalbert Löbl's son Hugo joined the company. He promoted strongly the move toward electro-technical material.

Kramer and Löbl introduced the Bakelite molding process in Czechoslovakia. The company became the dominant manufacturer of electrical accessories and exported products to many countries all over the world.

annexation of Czechoslovakia by Nazi Germany, the company was confiscated. The Jewish owner, Hugo Löbl, was dismissed and replaced by Hans Büllmann. From 1940 production was fully focused on war industry.

After World War II, industry was nationalized in Czechoslovakia. Electro-technical companies were merged and renamed to Elektro-Praga. The plant in Jablonec nad Nisou had the monopoly for manufacturing electrical accessories. Production grew steadily and from the 1960s export started to other countries.

State owned enterprises were privatized. In 1993 Elektro-Praga in Jablonec nad Nisou became part of the Asea Brown Boveri (ABB) concern.


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