Danish telephone plug
Encyclopedia
The Danish telephone plug is the special flat round telephone plug used in Denmark
for POTS
(analog) telephone lines and some "raw copper" (for ADSL etc.) telephone lines. The plug has 3 flat pins arranged at right angles to each other. This plug is used in few if any other places in the world, and most equipment now made uses the US/International RJ11 socket on the device end and includes either a cable with the Danish Telephone Plug at the wall end, or a standard RJ11 to RJ11 cable with a bundled Telephone Adapter.
Each pin is 13 millimetre long, 10 millimetre wide and about 2 millimetre thick, compatible with one of the historic types of blade plugs
. The two signal pins are 14 millimetre apart while the ground pin is about 11 millimetre above the center of the two signal pins.
In practice, 5 variants of the plug are currently being made:
The 3-pronged Danish Telephone Plug is a simplified form of an older 5 pronged plug, where the two extra pins (vertical, above and further apart than the signal pins) connected to a customer premises long life battery that provided power for telephones before the introduction of "automatic dialing" (the ability to place calls without operator assistance).
Also in installations of similar age, a mechanical switch was sometimes installed behind the socket to allow manually switching the phone line between sockets in two locations within a building.
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
for POTS
POTS
POTS may refer to:* Plain old telephone service, basic wireline telecommunication connection** POTS codec, a digital audio device** DSL filter, also known as a POTS filter* Postural orthostatic tachycardia syndrome, a medical condition...
(analog) telephone lines and some "raw copper" (for ADSL etc.) telephone lines. The plug has 3 flat pins arranged at right angles to each other. This plug is used in few if any other places in the world, and most equipment now made uses the US/International RJ11 socket on the device end and includes either a cable with the Danish Telephone Plug at the wall end, or a standard RJ11 to RJ11 cable with a bundled Telephone Adapter.
Technical description
The plug consists of two vertical and one horizontal flat pin, arranged like 3 sides (left, right and top) of a rectangle. The two vertical pins carry the same tip and ring signals used in other countries. The third pin (top, horizontal) used to be connected to ground and was occasionally used with switchboards, but is now generally unused and left unconnected.Each pin is 13 millimetre long, 10 millimetre wide and about 2 millimetre thick, compatible with one of the historic types of blade plugs
Electrical connector
An electrical connector is an electro-mechanical device for joining electrical circuits as an interface using a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or...
. The two signal pins are 14 millimetre apart while the ground pin is about 11 millimetre above the center of the two signal pins.
In practice, 5 variants of the plug are currently being made:
- A completely flat wall socket (pictured) 50×50 millimetres (almost 2×2 inches) with the 3 flat holes in the middle. This design matches the look, junction boxes etc. of other Danish wall outlets (such as those for AC power). It supersedes an earlier round model which had a slightly recessed circular depression where the plug goes.
- A regular plug (pictured), with the 3 pins going into the wall and the handle part of the plug being a flat 28 millimetre disc protruding only about 12 millimetre from the socket. The telephone cable generally exits the plug at the bottom. The plug has a slightly larger diameter (33 millimetre) for its outermost 5 millimetre, thus providing an easy grip. This design supersedes an earlier model which protruded about 18 millimetre from the socket (pictured).
- A combination plug/socket, where each pin of the plug mechanically extends into the connecting part of each hole in the socket. The entire plug/socket is round and extends 18 millimetre from the socket it is inserted into, making it the same size and shape as the earlier variant of the regular plug. The combination plug/socket also has the larger diameter at the outer (socket) edge for easier grip.
- A round socket used at the end of extension cables. This is also the same size and shape as the earlier variant of the regular plug, but there are no pins and the socket holes are on the side where the pins would otherwise be.
- A crudely made telephone adapter (pictured) which combines a combination plug/socket (as above) with an RJ11 socket in a single plastic housing. This mass-produced adapter has a larger diameter than its non-adapter cousins, for no apparent technical reason.
History
Unlike in some other countries, this telephone plug was introduced long before any liberalization of the telephone market occurred. Until the mid 1980s, all legal telephone equipment with this plug was rented, purchased or at least approved from the regional telephone companies or the government.The 3-pronged Danish Telephone Plug is a simplified form of an older 5 pronged plug, where the two extra pins (vertical, above and further apart than the signal pins) connected to a customer premises long life battery that provided power for telephones before the introduction of "automatic dialing" (the ability to place calls without operator assistance).
Also in installations of similar age, a mechanical switch was sometimes installed behind the socket to allow manually switching the phone line between sockets in two locations within a building.