A communication system for communicating between a central control unit and a plurality of controlled units, all interconnected by a single communication channel, wherein communication is time multiplexed with control words being transmitted in each direction during each time interval allocated to each separate controlled unit. The control words are transmitted during half-cycles of a periodic clock signal of one polarity, while data from the controlled units may be transmitted to the central control unit only during half-cycles of the periodic signal of the opposite polarity.
An interface is made for a device for the exploitation of electrical signals between a receiver of this device and a device for the exploitation of these signals. The interface is capable of sending, alternatively, signals received by the receiver to an external circuit and signals delivered by the external circuit to the exploitation circuit. It is shown that this approach can be used to resolve problems of the scrambling and unscrambling of audio-visual signals.
First and second redundant command signals are formulated in parallel-by-bit digital format by two ganged wafer switch sets in a control unit. The first redundant command signal is stored in a shift register and subsequently strobed out, by clock pulses received from a remote unit, and transmitted to the remote unit in serial-by-bit format where it is stored and used to control the remote unit. The command signal is subsequently clocked out of the remote unit and returned to the control unit in serial-by-bit format where it is compared against the second redundant command signal to insure that the remote unit has responded to the proper command. A renewable timer is reset by the clock pulses. If the clock pulses are interrupted for more than a predetermined time the renewable timer times out and indicates a fault.
A communications system in which control or access to a channel is distributed among the several transmitting-receiving station linked by the channel rather than being centralized or under a master station control.
A system master unit is connected to a 24V AC power source. One or more slave units is connected to the master unit by a power/communication line. Bulk capacitance in the master and slave units stores power during a power source positive half cycle. When the source voltage is higher than the bulk capacitance voltages, power is delivered to the loads, during which time communication cannot take place over the power/communication line. During the power source negative half cycle, the power/communication line is disconnected from the AC power source and is then used for communication between the master and slave units. System power is delivered from the energy stored in the bulk capacitance.
A plurality of stations (S), for instance measuring probes, preferably comprising respective microprocessors (KL), are connected successively to a common two-wire line (SL). Supply voltages and synchronization signals are distributed through this line (SL) from a central unit (CU), and at the same time a full duplex communication between single stations (S) and the central unit (CU) is enabled.
