GERMAN, WWII, WW2, Lichtsprechgerät 80/80

This is a 2-way audio communication equipment.
The signal is transferred on a light beam from a 5-watt bulb.

The light beam is modulated with a light phase modulator.
The light beam is AM-modulated with a moving prism.
The position of this prism is manipulated of the transmitter audio amplifier.

Red or IR filter can be inserted in the beam.
Receiver and transmitter have one lens each.
Light detector is placed 250 mm behind the receiver lens.
Diameter on the light detector is less than 1 mm,
so the direction of the unit is very important.
Diameter of the light beam is only 1.4 meter at 250 meter from the transmitter lens.
This will give a diameter of 7 meter 1 km away.
An RV2P800 tube is connected directly to the light detector as a preamplifier.
Diameter on the receiver and transmitter lens is 80 mm.
Manufactured by Carl Zeis Jena.

Optic	Receiver - 80 mm Transmitter - 80 mm
Tubes	Receiver, 3 - RV2P800 Transmitter, 2 - RV2P800
Detector	Thalofidezelle
Filters	Reed, visible Reed, IR, invisible
Range	4 km without filter 4 km with reed filter 2-3 km with IR filter
Power	2 VDC, filament 4.8 VDC, bulb 50 VDC, detector 60 VDC, anode voltage

Here are pictures from the second 2-way test of my LiSpr-80’s.
The distance between station A and B was 2000 meters.
The test was done on the island Fur in Denmark 12. jun. 2004.

Egil adjust the direction of the optic at position A.

Station A is located on an old barrow.

Here is the direction finder of LiSpr.80.
The red area in the picture is the actual light beam transmitted from LiSpr-80.
This is the size of the beam at a distance of 2km.
The black rectangle at bottom of the photo is the transmitter modulation monitor.

This is the actual distance from position B to position A.
The light beam from station A can not been seen on the photo, but it can bee seen with the eyes.

Marie at position B.

The communication is very good.

We also tested communication with red filters
with good results. The light beam was invisible with red filters at 2km.

Here are pictures from the first 2-way test of my LiSpr-80’s.

I have worked on the equipment in one year before this test.
Both the optics and electronics are restored. A new power supply is also designed.
The power supply deliver all the voltages needed for operation of the LiSpr-80.
The distance between the two LiSpr-80 were 300 meters.

Egil at position A. The first signal received.

Marie at position B.

Egil have here switched on the reed filter.

Marie has fine-tuned the direction with the direction-finder optic.

Here is the light from position A. Here with white light.

These are pictures from the first test of communication to and from a reflex.

Remco Caspers have sent me this interesting information:

I am attaching some pictures related to the Li.Spr.80 that you may find interesting.
These were taken near Ohama Beach in Normandy in Wiederstands Nest 62 (W.N. 62) which
caused a lot of problems for the Americans on D-day (This is in front of the beach
sector where Frank Cappa took his famous photographs). This little bunker actually
used to house a Li.Spr.80 and was used for communication with the command bunker
further inland. In the first picture you can see the church spire of Colleville in
the distance, the command bunker with the other Li.Spr.80 was situated slightly to
the left of the church, currently obstructed by dense vegetation. The distance was
about 1500 m, so well within the range of the Li.Spr.80 although I can imagine that
during the bombardments on D-day, visibility must have been significantly reduced.

One of the surviving Germans described that before D-day, they often placed the
microphone of the Colleville station near a radio, so that they could listen to
music in W.N. 62! The second picture shows the slit through which the light beam was
projected. One of the survivors describes that when they abandoned W.N. 62 in the
afternoon of D-day, he actually carried the Li.Spr.80 with him, only to discard it
in the bushes halfway through the journey to the command post, it might still be there!
I found it quite interesting to find out that this piece of equipment actually played a
role during one of the most famous operations of the war.

Further equipment used on W.N.62 was a Torn.Fu.b1, used by an artillery observation
party to communicate with the battery placed about 6 km inland. Again the observation
post and small radio bunker still survive.

Lichtsprechgerat 80 in use. Adjustment of the optic unit.
It is important to adjust direction of the optic unit within 0.2 degree.