Kleiner Draht Lausch Empfaenger

[Funksammler]

Drahtlaushempfaenger Klein D.L.E. (kl)

The Drahtlauschempfaenger, or wire tap receiver must surely be one of the most compact pieces of equipment made for the Wehrmacht, measuring only 9 x 5 x 17 cm. Essentially a two stage audio amplifier, it uses two RL 2.4 P 45s to amplify the signals of telephone lines. The high input impedance of the receiver would not weaken the original signal strength of the tapped line, so the user would be unaware that he was being listened to.

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Figure 1: Circuit diagram

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Figure 2: Receiver construction

The set consists of the receiver and battery box which are linked together when in operation. The receiver, battery box and accessories were stored in a leather bag when not in use.

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Figure 3: Complete set in leather case

The receiver has all controls on the top section which was made out of bakelite. It has three controls: Left: On/Off switch and sensitivity control; Middle: Input balance control; Right: volume control. It has a three pin jack which can be used by either the standard headphones, or the smaller plug of the single telephone earpiece.

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Figure 4: Controls

Three spring loaded wire terminals marked e (earth), a and b (line connection) allow the receiver to be connected to a telephone line.

A lid on the bottom of the receiver can be opened for access to the two valves. The connections and locking pins to attach the battery box are mounted on the side of the receiver.

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Figure 5: Receiver and battery box with opened lids

To connect the set the earth terminal would be connected to a suitable earth, while the a and b lines would be connected to a two telephone wires to be tapped in to.

The battery box simply slides and locks onto the side of the receiver, three contacts automatically connect the two boxes. The battery box has the same size and has lids on top and bottom leading into two separate battery compartments, taking 3 V cells, very similar in size to current AA batteries. In the top section, eight cells are placed in series to make 12 V anode voltage. In the bottom section, the eight batteries are placed in parallel to make 3 V filament voltage. A resistor is used in series with the tube filaments to reduce this to 2.4 Volts.

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Figure 6 and 7: Receiver and battery box connected, ready for use

I have not found any anecdotes of their actual use, but it is likely that they were used by the Wehrmacht to tap into field telephone lines as well as by the Abwehr and secret police services to tap into the civil telephone net. As such the D.L.E. (kl) should be considered to be a small but significant piece of communications equipment.

The receivers do appear on the market from time to time but battery cases are extremely rare. As far as I am aware these are the only published pictures of a surviving battery case. I have yet to encounter the bag, but who knows somebody saved one to take their lunch to work…..

regards,

Funksammler

[ARYEH]

Draht Lausch Empfaenger

Great posting Funksammler - as usual highly informative and great photos.
The input circuitry has T- filter before the first transformer ..........
The following is from TM-E 30-45 Handbook on German Military Forces

3) Interception receivers, direction finders, and ground listen
ing sets.—........ An ingenious ground listening device is known to be in use.
It consists of a cylindrical aluminum container, at one end of which
are two terminals connected to the end of an internal winding.
The other end can pivot around an axis perpendicular to the axis
of the cylinder, forming a jaw firmly retained upon its seating
by a strong spring. The side of the cylinder carries two openings
diametrically opposite, allowing a telephone line to be held therein
by the jaw. The inside face of this jaw carries a moving armature
of a transformer core made of soft laminated iron. The spring
forces the moving armature against the fixed part of the trans-
former, thus closing the magnetic circuit. The external termi
nals are connected by a pair of wires to a low-frequency amplifier.
The telephone line, when inserted, acts as the primary of the
transformer. The apparatus can be easily put in place, and no
indication is given of its presence while it is in place or after it
has been removed.

The word GROUND does not mean ground-induced but ground as to differentiate from aeronautical etc. It would appear that an Induction Coupling probe as described above could have been used with the Draht Lausch Empfaenger. Does anyone have more info on the Induction Coupling probe? The modern day clamp on ammeters are derived from it.
Also interesting to note the very compact design, multiple use of 1.5v batteries (schematic has anode voltage listed as 24V though not 12V),etc.

Has anyone seen the movie "The Lives of Others", hi hi
Cheers
Aryeh

[B. Dietz]

Very nice.

[Yuri D.]

Funksammler, very nice and highly informative presentation. You are a treasure to this forum.

Please keep up your amazing posts.

Yuri


PS. I have seen "The Lives of Others", and it's a great movie.