Apparatus to control the direction of movement of a mechanism over a surface. The surface is provided with a plurality of substantially parallel strips of conductive material alternately connected to opposite terminals of a source of current supply. The mechanism has a plurality of conductive discs or wipers so disposed that at least two of the wipers contact a pair of the conductors which are each connected to oppositely disposed terminals. The mechanism also has driving means such as wheels for movement and a motor engaged through the wipers for propelling the wheels over the surface. The mechanism can move forwardly, rearwardly, laterally or in a zig-zag motion. Control means are provided between the motor and the driving means so that the direction of movement may be varied in response to the voltage across the alternate conductors engaged by the wipers.
A circuit arrangement for transmitting and receiving radio signals includes an amplification device with an output for transmitting signals, an input for receiving signals and a supply line, and an antenna for transmitting and receiving signals. The antenna is connected to the output of the amplification device. The output of the amplification device is an input for signals received via the antenna, and the supply line is an output for received signals that are converted to the supply line by the amplification device.
