Apparatus for indicating whether one or more objects are in motion

Apparatus for indicating whether one or more objects, for example, threads, strips or the like, are in motion, said apparatus including a plurality of signal generating means, one signal generating means associated with each object to be detected, each signal generating means generating an electric signal upon detection of movement of its associated object;

• means connecting said plurality of signal generating means together in a series circuit;
• a first signal amplifier coupled to the first end of said series circuit;
• a second signal amplifier coupled to the second end of said series circuit;
• a coupling device connected to said connecting means to successively ground the connections between the signal generating means in said series circuit;
• first gate means having a first input connected to the output of said first signal amplifier, a second input connected to the output of said second signal amplifier, and an output connected to said coupling device, said first gate means interrupting the successive grounding of the connections between the signal generating means upon simultaneous receipt of a signal at both inputs of said first gate means, which indicates a signal from at least one signal-generating means on each side of the grounded connection.