Abstract: The invention pertains to an uninterruptible power supply (UPS) with a rectifier supplied with power by a power network, connected to an intermediate circuit having a battery as well as to an inverter connected to the intermediate circuit for supplying an interruption protected power source. The control for the main input rectifier and the inverter is supplied using two secondary rectifiers, whose outpus are connected in parallel through decoupling diodes. The first secondary rectifier which supplies power to the control unit in normal operation, is connected to the input power network.

Abstract: A signalling apparatus has at least one transmitter in a transmitter assembly for transmitting a signal by impressed current to several spatially separated receivers. A series circuit of threshold members is connected to the output terminals of each transmitter, the number of members corresponding to the number of receivers. The input of each receiver is connected to a threshold member; the receivers are therefore connected in series on the input side. It is ensured thereby that the same current flows through all receivers. In the event of a failure of a transmission line or a receiver, the current continues to flow through the associated threshold member so that signal transmission to the other receivers continues uninterrupted.

Abstract: A method for controlling the voltage and the load distribution, as well as for synchronizing, of several inverters the outputs of which can be connected to a common bus bar in which, for each inverter, a simulated control variable is formed and is compared as to amplitude and phase with a reference voltage which is the same for all inverters.