Siemens Aktiengesellschaft

Steven Moustakas

Hans-Hermann Witte

Jan Goerne

Viktor Bodlaj

Hans H Witte

Joseph Kozilek

A circuit arrangement is provided for testing a passive bus network system which comprises stations which are connectible to a coaxial cable segment via media adapter units, the stations realizing the data packet exchange via the coaxial cable segment with carrier sense multiple access with collision detection access method. In conjunction with a status receiving device which monitors the transmitted data packets, the passive bus network system is monitored by the data transmitter and the data receiver in view of the presence of the line terminating impedances, the proper connection of the media adapter units to the transmission medium, as well as the transmitting and receiving functions and the collision recognition and state of the collision recognition circuit.

Circuit arrangement for testing a passive bus network with the carrier

In a data network distributor adapted to connect a plurality of data stations with each other directly, and with remote stations over a network bus, a selective voltage supply system allows units shared in common with the local data stations to be powered only as needed, and to draw power from the individual data stations requiring service. Individual power sources in each data station are connected to a common line through decoupling diodes and current limiting resistors, and the common line supplies a plurality of voltage supply units which are operative to supply power to commonly used units as needed, including transmitting and receiving units for the network bus, a data diversion device for diverting local communications from the network bus, and a common control circuit for data collision recognition.

Selective voltage supply system for data network distributor

In an asychronously operating optical data bus:

Method and apparatus for recognizing data collisions in an optical data

An optical data bus with a statistical access method for the transmission of data between transmitters and receivers in the form of NRZ data provides that every transmitter of a subscriber contains a Manchester encoder which Manchester encodes the NRZ data and deposits such data onto the bus in a Manchester-encoded form. The receiver of every subscriber contains a Manchester decoder for the reacquisition of the NRZ data from the Manchester encoded data and contains a clock recovery device which recovers the clock contained in the Manchester-encoded data. Such a Manchester decoder with the clock recovery device can be constructed in a very simple manner and such a simple structure is disclosed. A very simply-constructed bus state recognition device is also included.

Optical data bus having a statistical access method

A device for recovery of a synchronized clock signal from a signal sequence, in particular a random sequence, clocked at a specific frequency. The device includes a clock generator which by itself generates clock signals whose phase and frequency are tuned to the specific phase and clock frequency of the signal sequence, and which is triggerable externally by specific signals derived from the signal sequence in order to synchronize its phase and frequency with the phase and clock frequency of the signal sequence. The clock generator includes preferably a monostable multivibrator whose output signals are fed back delayed to the input serving as trigger input.

Device for recovering a synchronized clock signal from a signal sequence

A device and method for reducing level dynamics in an optical star bus transmission system is disclosed wherein variable electrical resistors are connected in series to the electro-optical transmission elements of the system transmitters and are selectively adjusted so that differences in the signal power levels at a selected system receiver are reduced to zero, and hence the differences in the signal power levels at the remaining system receivers are substantially reduced. Furthermore, variable electrical resistors are connected in series to the gain controlling resistors of the amplifier stages of the receivers of the system so that when any specific transmitter couples power into the system, differences in the output levels of the amplifier stages of the receivers are also substantially reduced. The invention may be practiced with trimming potentiometers.

Device and method for reducing level dynamics in an optical transmission

If data from more than one subscriber circulates on a bus link in an optical bus network structure in which access of the subscribers to the bus is not synchronously controlled, data collisions can occur. In order to guarantee a high data throughput on the bus, these data collisions must be avoided insofar as possible or must be quickly perceived. A circuit for identifying possible data collisions determines whether the bus is free for a subscriber wishing to transmit, and which permits collisions on the bus to be quickly identified and corresponding measures to be quickly initiated to prevent further collisions. The present invention enables a subscriber to a bus system to distinguish between a data collision and normal transmission errors. This distinction is made by concluding that a collision has occurred only when the bit error frequency is substantially higher than the probabilistically determined normal transmission error frequency.

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Munich, Germany

Steven Moustakas