Abstract: A manual call point with an e-paper display is described herein. One device includes an e-paper display configured to display an image that represents a status of the manual call point, a memory, and a processor configured to execute executable instructions stored in the memory to determine a change in the status of the manual call point, and change the image displayed by the e-paper display in response to the determination that there is a change in the status of the manual call point.

Abstract: An alarm system control center has subscribers connected to it by a two-wire line. The subscribers receive via the two-wire line both a power supply voltage and communication messages in the form of pulse trains impressed on the power supply voltage as voltage modulation. Each subscriber includes a constant current circuit which is connected to the two-wire line and which is used to charge a storage capacitor with a voltage regulator coupled to it. In order to reduce communication errors, a transformer is provided to reduce power supply voltage to an internal value which is lower than the than the power supply voltage at least by the voltage swing of the pulses of the communication messages on the two-wire line.

Abstract: An alarm system control center has subscribers connected to it by a two-wire line. The subscribers receive via the two-wire line both a power supply voltage and communication messages in the form of pulse trains impressed on the power supply voltage as voltage modulation. Each subscriber includes a constant current circuit which is connected to the two-wire line and which is used to charge a storage capacitor with a voltage regulator coupled to it. In order to reduce communication errors, a transformer is provided to reduce power supply voltage to an internal value which is lower than the than the power supply voltage at least by the voltage swing of the pulses of the communication messages on the two-wire line.

Abstract: A building control or danger warning system includes a two-core circular bus for voltage supply and for communication with bus user circuits connected to the cores of the circular bus. The bus user circuits are looped-into the circular bus via FET (field effect transistor) polarity-reversal protection bridges, thereby simplifying connection of the bus user circuits to the circular bus. A bus user circuit is located between d.c. connection terminals and connected in parallel with two protection bridges. The bus user circuit measures the voltage conditions and polarity of the a.c. voltage input terminals of the bridges. According to the results of the measurement, the bus is relayed to the subsequent bus user circuit.