Flap cabinet

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Flap cabinet for 50 telephone users (around 1900)
Flap cabinet for 15 lines

Flap cabinet is the name for a telephone manual switching device . Until the telephone network was fully automated , flap cabinets were used to establish the voice connection between two telephone subscribers. For this purpose, each intercom was assigned a handle and an electromagnet with a simple flap mechanism. At that time, every telephone set was equipped with a local battery . If someone wanted to have a conversation, he operated the crank inductor on his telephone set. With this, he generated an alternating current that attracted “his” electromagnet on the flap cabinet. This released a metal flap that fell down, telling the young woman from the office that she wanted to connect. This connected her speech kit to the caller's telephone via the jack . What happened next was precisely regulated in Germany by the Reich Telegraph Administration by means of service instructions:

  • Office: Office here, what is popular?
  • Participant: Desires to speak with number 44

If the desired participant was free:

  • Office: Please call
    (the operator established the connection to the B-subscriber using a pair of cords )


  • Office: Already occupied, I will report when free
  • Participant: Understood

The caller announced the end of the call to the operator by pressing the crank inductor again. The operator cut the connection and returned the flap to its original position by hand.

The functionality of the flap cabinet was simple and yet very effective:

  • The signaling of the connection request did not consume any electricity from the local battery.
  • The connection request was easily saved. It was not necessary for the operator to keep an eye on the closet.

The operators in large local networks initially had to do their job while standing. Later, with the introduction of multiple fields, they were also allowed to sit. With the rapidly increasing demand for telephone connections at the beginning of the 20th century, the handles and drop flaps were made smaller and smaller. One operator could manage up to 10,000 connection options .

From 1895, with the introduction of central battery operation, incandescent lamps were also used for signaling . The flap cupboard became a light bulb cupboard .

There have also been attempts in the meantime to accommodate the handles and signaling devices in tables that were worked on from two sides. It is known from Amt III Berlin that the tables there were 85 meters long and contained 570,000 handles. A little later they went back to the cabinet design.

With the expansion of the automatic switching centers in Europe , beginning in Hildesheim from 1908 , the flap cupboard became less and less important. At the Deutsche Bundespost , the last flap cabinet was taken out of service on April 29, 1966 in Uetze, Lower Saxony . There, six operators in three shifts had connected 374 participants with one another and with the outside world around the clock. When Deutsche Post the GDR the last switchboard went in 1987 in Falkenrehde out of service.


In Austria, the first telephone system with manual exchange was put into operation on December 1, 1881 in the 1st district of Vienna . Automation began again in Vienna on April 1, 1905, where it was completed on June 27, 1925. The last manual switchboard in Austria was switched off on December 14, 1972. The term "flap" for an extension number is still used in Austrian today .

United States

In the United States , the last flap cabinet for local calls was taken out of service in 1983. It was located in Bryant Pond, Maine. For special cases, flap and bulb cabinets were also in use for a longer period of time, at the AT&T Marine Operator ( coastal radio stations ) until the 1990s.


  • Regulation H.Dv. 95/27, The flap cabinet for 10 lines (draft), 1926

Web links

Individual evidence

  1. End of an era for Maine crank phones. Retrieved April 16, 2019 .