Lichtsprechgerät 80/80
LiSpr 80
Some technical information.


I work here at my lab with phone connection over the LiSpr80.
Plans a video that shows phone connection over the LiSpr80.

It was new and unexpected problems when phones were connected.
I got feedback issues when the telephones were connected.
It became important more correct adjustment of the modulators and volume control.
This equipment is not easy to use. It requires skilled communications people to get this to work,.

Here we see light modulator image in the sight.

This is what we see during the modulator adjustment.
On the underside of the optic device there is an adjustment button.
We adjust to the maximum signal.

Power for a 2.4V LiSpr80.

I have got a new electronics unit for 2.4 Volt lamp.
I will now make a power for it.
It needs 2V for tube heater, 2.4V for the lamp,
50V for the light cell, 60V for anodes and -1.5V for grid bias.


I use an Ikea tray as a power box.
Two three lists are glued to the box.

A fiberglass plate is screwed onto the box.

Contacts are made

The cables are sewn together with a special cable sewing thread.

The cables are mounted.

The cables are soldered to the power. .

The power is made ready. The electrical voltages are fine tuned.

Everything is ready and I will now test everything.
It was excellent. The result will be shown on youtube.

LiSpr80 Bunker

New photo cell

All the original light cells are unfortunately defective.
Therefore, we need to replace with a new cell.

Got three optics devices. Should show some pictures of these here.

Have received three LiSpr8080. They are collected by Jens Henrik Mo.
I will now try to build two working units.

Here we see two LiSpr80 light bulbs.
The yellow mark is 2.4 Volt.
The non-marking is 4.8 Volt.

The underside of the serial no. 217676 from 1940.
You also seen mounting mechanism for the stand.

The underside of the serial no. 197676 from 1938.

The underside of the serial no. 187856 from 1937.
This has a totally different fastening to tripod than the other units.

Close up of the tripod mount.
Absolutely amazing design. Super Accurate setting the height and angle. .

Here is the empty chassis ready to be built up with components.

Here are the specially designed lamp and light housing.
The accuracy of filament must be extremely accurate.
The light from the lamp reaches 5km.

This is the advanced modulator.
The light from the bulb goes into the small hole to the right and
come out into the big hole on the right.
Lights out is modulated with the audio from the input signal.

The four electromagnets move the small prism.


When I would get LiSpr80 operative I found that all light detectors were defect.
I therefore had to mount a light transistor.
I drilled a hole and soldered it.

To provide transistor proper working condition I had to install some additional components.
It does not look quite good, but I should have the equipment operational quickly.

1 Improved noise with 100uF from the negative grid voltage (21) to gnd.
2 Node # 18 was converted to constant 12V with zener diode.
3 capacitors 47uF and 3.3uF from node # 18 to gnd.
4 Resistor on 27K supplies power to the transistor from node No. 18
5 Resistor on 100K and 82K supplies power to node no.18.

Here is the calibration equipment.
At the top is a reflex, at the bottom is an LED that
is modulated with 400 Hz square pulses.
This is placed 500 meters from the LiSpr80 to be calibrated.