Non Radio covert communications

[Lightspeed]

Here's a crazy idea for a simple, covert, non-radio signalling device for communications between fixed locations.

Mount one of the high intensity LEDs in a length of straight metal tube and battery power it via a simple press to make non latching switch. The longer and smaller diameter the tube, the tighter the viewing angle, so the signal will effectively be rifle shot to the desired target.

Such a device could be mounted in a fixed orientation within a roof with the tube exiting through a gable wall etc appearing to be some kind of overflow pipe from outside. It would be aimed at the target receiving location’s fixed observation position.

A portable version could be constructed along the lines of a rifle with the tube mounted on a rifle stock and aimed with an iron or better still a telescopic sight.

Messaging would be by on off flashes. That code would ideally be of our own devise. LED’s which have variable colours could add a third dimension to the signalling possibilities.

Application might be between houses separated, but with clear line of sight between them, between a base and surrounding observation posts. Possibly such a system could be deployed give warning on approach routes to the base whereby from very specific observation points the lamp could be visible (green safe to proceed, Orange , green etc)

Advantage of the system: Very covert, transmitter tube can be hard wired to operate at a considerably remote location form the operator. Simple to construct, durable materials, Low power consumption

Limitation: the system that only work in low ambient light, and in clear, non foggy/rainy/ snowy conditions. Requires electrical supply. Only detectable from very precise locations. Requires ability to decipher transmitted codes.

Employing a mini laser diode would allow the device to function in higher ambient light but is not really suitable as it'd be damaging to the viewers eyesight.

As stated at the start, a crazy idea, but maybe useful to someone one day?