Orientation layers of monomeric or polymeric liquid crystal layers having any desired azimuthal orientation direction and a tilt angle are produced by irradiating at an angle differing from the normal to the surface photopolymers orienting parallel to linearly polarized light. The control system also provides a cool-off period after a lamp-off cycling event is detected during which time restarting of the lamp is inhibited. The device for transforming the high-frequency electrical signals supplied by the photoelectric receiver into low-frequency measuring signals can include at least one switch whose switching frequency is controlled by a control frequency whose frequency is higher or lower than the modulation frequency by the amount of the low-frequency measuring signal. When transmitting the data, transmitters in certain adjacent cells throughout the geographic area may employ slightly different transmit parameters to provide slightly different transmission signals.