PRECISION SETTING OF CURRENTS AND REFERENCE VOLTAGES

This patent describes a regulated power supply system designed for use in transceivers for Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) communications networks. The system provides a precise method for setting threshold voltages used in collision detection.

Key technical aspects include:

• Precision Regulation: A single zener diode is used as a reference to regulate two distinct power supply outputs through different feedback mechanisms.
• Collision Detection: The transceiver monitors the signal on a coaxial cable and uses two precise threshold voltages to distinguish between no signal, a single-source signal, and a collision (multiple simultaneous signals).
• Voltage Feedback: The regulated power supply output is controlled by a feedback signal derived from a sampling point in the threshold-setting circuitry, rather than just internal power supply monitoring. This ensures the threshold voltages remain at the required levels despite variations in other components.
• Transceiver Protection: The device includes guard circuits to disconnect the transmitter from the network if it becomes "stuck" in a transmitting state, and it incorporates collision detection test circuitry to verify proper operation of the transceiver.