Abstract: An interface module may have a customized circuit to enable an operation using modulated signals, which are free of direct current, by way of a serial bus interface. To effect the communication, adapted connecting means are also needed to connect a subscriber to a two-wire line bus. An interface chip achieves a user friendly connection. Starting from its terminal side going toward the two-wire line bus the interface chip features a transformer and, with it, in series a parallel connection consisting of a receiver and a transmitter. Furthermore, in the interface chip, a comparator and a voltage source are provided, which transmit, as a function of the level of the modulated signals, a blocking signal to a circuit used to modulate and demodulate the signals. To release the signals to be transmitted, the customized circuit transmits an enabling signal to the transmitter.

Abstract: A user-friendly interface module which makes possible a simple structural attachment to a standardized bus interface having good suppression of interferences as well as a non-volatile termination of a two-wire line bus. The interface module includes a housing with an external ground terminal clip and four terminals. The interface module also includes a resistive divider to terminate the two-wire line bus as well as a multicore cable. Communication is established, for example with a microprocessor, via the multicore cable. The interface module can be used in a network system with programmable controllers.

Abstract: The invention relates to an interface module for the bidirectional transmission of data streams in a data network with separate power supplies for the individual bus stations. According to the invention, means are provided for bridging the bus station, preferably via normally closed contacts of a relay connected to the supply voltage and for simulating the ready condition if the power supply in the interface module fails. The latter consists of an OR circuit which is supplied on the one hand, via an operational amplifier and an RC section, with a constant delay and, on the other hand, via an optical coupler taking off the input signal, and a Schmitt trigger connected thereto.