Level shifting multiplexing circuit for connecting a two conductor full duplex bus to a bidirectional single conductor bus

A circuit for connecting a two conductor full duplex bus referenced to a first supply voltage to a single conductor bidirectional half duplex bus referenced to a second supply voltage:

• a first field effect transistor (FET) having a first drain connected through a first resistor to the first supply voltage, a first source connected to ground, and a first gate configured to connect to the single conductor bidirectional half duplex bus, the first drain configured to connect to a reception conductor of the two conductor full duplex bus;
• and
• a second FET having a second drain connected through a second resistor to the first gate, a second source connected to ground, and a second gate configured to connect to a transmission conductor of the two conductor full duplex bus.

A level shifting multiplexing circuit for connecting a two conductor full duplex bus referenced to a first voltage supply to a single conductor bidirectional half duplex bus referenced to a second voltage supply, the circuit comprising:

• a first switching means for switching a low logic level to a reception conductor of the two conductor full duplex bus when a first switching voltage threshold is exceeded on the single conductor bidirectional bus and switching a high logic level when the first voltage threshold is not exceeded on the single conductor bidirectional bus;
• a second switching means for switching a low voltage and high voltage relative to the first switching voltage threshold to the single conductor bidirectional bus based on a transmission conductor voltage of the two conductor full duplex bus and logic level transmitted by a device connected to the single conductor bidirectional bus.