Considering these voltage levels on the bus, there are thresholds that most transceivers abide by, with some companies deviating slightly from the norm. Because it is a single-ended communication scheme and the thresholds cannot be set by a voltage differential, these thresholds are based on a percentage of the battery voltage in the system. These thresholds determine when the bit is considered “recessive” or “dominant”. Recessive and dominant are just different ways of saying high and low (respectively) on the bus. The naming convention comes from the concept of how the bus and transceivers interact with each other and how the signals are generated inside the IC.

From a high level, a cluster is equivalent to an open-drain circuit, meaning the bus requires a pullup resistor and all the nodes are passively connected to the bus through transceivers. When prompted, the transceivers control the voltage levels on the bus. The pullup resistor ensures the voltage levels on said bus meet or are close to the battery voltage level when the TXD control of the transceiver is in the off state. Once the transceiver becomes active and the TXD control transistor turns on, the bus is driven low, to nearly ground level and the high state is overwritten. Therefore, the bus is pulled up high when the transceiver is off or in a passive state, hence “recessive”. When the transceiver TXD begins conducting and becomes active, the bus is driven low, hence “dominant”.