Composite interface circuit

A composite interface circuit including a bidirectional single-conductor bus, for coupling together (a) a first full duplex universal asynchronous data communication interface having a first receiver conductor (Rx1) and a first transmitter conductor (Tx1) and (b) a second full duplex universal asynchronous data communication interface having a second receiver conductor (Rx2) and a second transmitter conductor (Tx2), the composite interface circuit comprising:

• a bidirectional single-conductor bus being coupled by a first pull-up resistor (R1) with a first direct current (“DC”) input current source having a first voltage (V1);
• a first switching circuit including a first transistor (T1), the first transistor (T1) being coupled with the first pull-up resistor (R1) and with the bidirectional single-conductor bus;
• a second switching circuit including a second transistor (T2), the second transistor (T2) being coupled by a second pull-up resistor (R2) with a second DC input current source having a second voltage (V2), the second switching circuit further including a voltage divider coupling the second transistor (T2) with the bidirectional single-conductor bus;
• wherein the first switching circuit is configured for being coupled with a first transmitter conductor (Tx1);
• wherein the second switching circuit is configured for being coupled with a first receiver conductor (Rx1);
• and
• wherein the voltage divider includes a third resistor (R3) and a fourth resistor (R4), and wherein the third resistor (R3) is coupled between the fourth resistor (R4) and the bidirectional single-conductor bus, and wherein the second transistor (T2) is coupled with the voltage divider at a first node between the third resistor (R3) and the fourth resistor (R4).