Directly to the two connected with the door circuit will burn, so why not.
OC gate is only active low, "high" is high impedance state. Is this feature, so that they can simply achieve the "line or", and get a wide range of applications.
The open collector of the gate circuit can be made "line and" or "line". The output of the two doors in the figure can be seen as two transistor open circuit connected together, when the two transistors at the same time cut off or saturation when no problem. Considering a cut-off, another saturated, cut-off transistor does not flow through current, so no problem; saturated triistor is limited by resistor R1, ignoring saturation voltage drop (0.7V), I = Ucc / R1, so there is no problem.
Is a TSL gate (tri-state gate output circuit).
Three-state output circuit is a high level, low level and high impedance three output state of the gate circuit, also known as three-state gate output circuit. In the solid state machine board circuit, "I / O" board circuit, in addition to the above several combination of gate circuits, three-state gate circuit is also essential.
Three-state gate circuits are TTL three-state gate circuit and CMOS three-state gate circuit.
