The HD151015 is an IC which consists of 9 bus transceivers (three state output) in a 24 pin package. Signals are transmitter from A to B when the direction control input (DiR) is at a high level, and from B to A when DiR is at a low level. When the enable input ( G) is high, A and B are isolated. And this product has two terminals (V CCA, VCCB), VCCA is connected with control input and A bus side, VCCB is connected with B bus side. VCCA and V CCB are isolated. Consequently, it is best to change the level in case of two supply voltage coexist on one board and application of power management.