The field telephone lines of a 10-line switchboard can be connected three ways. The first way is to connect the lines directly to the 20 terminals lined up along the top. Each line has an “a” and “b” wire. The terminal pairs are numbered 1 to 10, left to right.
For lightning protection, the individual field telephone lines are first terminated on the “a” and “b” Außenleitung terminals of a Feldblitzableiter panel. Wires can the be connected to the “a” and “b” Innenleitung terminals on the Feldblitzableiter panel, with the other end of the wires connected on the “a” and “b” terminals on top of the switchboard.
The second and third way is to connect the lines using an Abspannleiste (or Anschlussleiste). The Anschlussleiste typically hangs from the Abspannbock which is a structure used to terminate field telephone lines. The Anschlussleiste has 20 terminals for terminating 10 pairs of telephone lines, 1a/1b to 10a/10b. At the center of the Anschlussleiste, is a 30-pin socket for a Verbindungskabel plug.
The Verbindungskabel is a 30-conductor cable with 30-pin plugs at each end. Lengths vary, but the Verbindungskabel can be about 30 feet long.
The plugs have 30-pins, but only 20 are used. Pins are lettered in rows “a,” “b,” and “c.” Row “c” is not used. Each pin in rows “a” and “b” is numbered 1 to 10. This corresponds to the terminals on the Anschlussleiste. Each “a” and “b” terminal on the Anschlussleiste is wired into the “a” and “b” sockets for the Verbindungskabel plug.
The second way to connect phone lines uses the other end of the Verbindungskable which is plugged into a 30-pin socket on a Kammleiste. The Kammleiste has 20 flat metal fingers that clamp under the 20 terminals on a 10-line switchboard. Each finger pair is numbered 1a/1b to 10a/10b.
The third way to connect phone lines also uses the 30-pin plug on the other end of the Verbindungskable. This plug fits in a 30-pin socket inside the switchboard. The socket is wired to the 20 “a” and “b” terminals on the top of the switchboard.
For lightning protection, the other end of the Verbindungskable, can be plugged into the Außenleitung 30-pin socket on a Feldblitzableiter panel. Another Verbindungskable can be plugged into the Innenleitung 30-pin socket on the Feldblitzableiter panel, and the other end plugged into the Kammleiste or the 30-pin socket inside the switchboard.
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WW2 German Field Telephone Equipment 