A data telemetering system includes a plurality of remote transmitter units connected via an alternating current power supply mains to a central receiver. Each cycle of the line voltage is divided into a plurality of time slots, and each transmitter transmits its data in a separate time slot assigned to it. The data is binary multi-bit digital data, and one bit is transmitted by each transmitter in its assigned time slot during each cycle of the line voltage.
When operating adjacent ultrasonic proximity switches, faulty output states can occur due to mutual interference (e.g., the incorrect allocation of echo signals). To solve this problem, it is known to adhere to standard mounting specifications as well as to apply parallel or serial synchronization. Ultrasonic proximity switches with an enabling output and a microprocessor are improved by inserting a circuit arrangement between these two elements, which, based on synchronizing pulses, produces a change in potential from high to low at the enabling output. By connecting the enabling outputs of several proximity switches constructed in this manner and operated adjacent to one another through a shared line, an improved operation with parallel and serial synchronization is possible without external control (i.e., automatically). The low potential state produced by an ultrasonic proximity switch at its enabling output is supplied via the line to the remaining connected ultrasonic proximity switches. While the line is at low potential, at least one proximity switch is not yet ready to transmit, that is only the change to high potential enables the parallel synchronization or, alternatively, introduces serial synchronization.
