An optical data distribution network including a plurality of drops and apparatus for distributing optical data signals to the plurality of drops wherein each drop has listen-while-talk capability is disclosed. Each drop comprises a single length of optical fiber for propagating transmit and receive optical signals between a directional coupler and the distributing apparatus. The directional coupler is operative to direct the transmit optical signals from an optical transmitter to the single length of optical fiber and to direct the receive optical signals from the single length of optical fiber to a first optical receiver. Each drop further includes a second optical receiver coupled to the directional coupler for receiving optical signals transmitted by the optical transmitter as directed to the second optical receiver by the directional coupler.

Simultaneous transmitter operation in a radio network is prevented by monitoring the signal received at the control position from the transmitter of the apparatus, this signal being delayed by the passage down land lines connecting the control position to its transmission antenna and the receiver to its control position. If a signal is received within a known time period from the time of commencement of a transmit action then it is assumed to be a signal from a remote transmitter and the operation of the local transmitter is aborted to prevent interference. The system is particularly useful where land lines and consequent time delays are present between the control position and the transmitter and the receiver and the control position.

The present invention relates to an apparatus for transmitting and receiving Manchester coded digital data for IEEE 802.3 Ethernet/Cheapernet type local area network. The apparatus mainly comprises, an isolation transformer, a signal converter with one end connected to one side of the isolation transformer, a receiver with its input connected to the other end of the signal converter, a capacitor located in the receiver and a transmitter with its output connected to the other side of the isolation transformer whereby the isolation transformer and the capacitor may isolate the external terminals from the main circuit. Moreover, the receiver and the transmitter can be integrally formed with a controller and thus to reduce the cost.

A diversity receiver includes first and second receivers, a first switch, a comparator, a second switch, and a controller. The first and second receiver have receiver antennas and generate demodulated signals and electric field detection outputs in accordance with received electric fields, respectively. The first switch performs switching between the demodulated signals from the first and second receivers in accordance with an output switching control signal and outputs a selected demodulated signal. The comparator compares the electric field detection outputs from the first and second receivers, respectively, and supplies the output switching control signal to the first switch. The second switch turns on/off a power source of the first receiver in accordance with a power source switching control signal. The controller receives the electric field detection output from the second receiver, calculates an average intensity of the electric field, and supplies the power source switching control signal to the second switch in accordance with the average intensity of the electric field.

Power stealing circuit receives data signals on its signal input terminal and diverts some power from the signal input terminal to its power output terminal to power another circuit. When the voltage on the signal input terminal exceeds the voltage on the power output terminal, positive supply power is "stolen" from the signal input terminal to the power output terminal. When the signal input terminal is below the power output terminal, the two terminals are disconnected. A similar circuit "steals" negative supply power. In some embodiments, a comparator compares the voltages on the two terminals and regulates the power stealing operation.