In CAN communication, how do CAN H and CAN L behave when not transmitting?

In CAN (Controller Area Network) communication, when the bus is idle and not transmitting any data, both the CAN High (CAN H) and CAN Low (CAN L) lines are at a voltage level of 2.5 volts. This configuration is known as the recessive state.

The differential signaling method used in CAN bus communication relies on the difference in voltage between CAN H and CAN L to convey information. In the recessive state, both lines being at the same voltage means that there is no dominant signal being transmitted. This balanced state allows the system to be ready for data transmission without interference, and it provides noise immunity by allowing the system to detect changes in the differential voltage.

Other voltage levels described in the other choices do not align with the standard behavior of CAN communication when the network is idle. For example, a 0-volt and 7-volt scenario does not reflect the characteristics of the CAN bus, and the same is true for the voltages used in the other options. Thus, the choice of 2.5 volts for both CAN H and CAN L accurately represents the typical idle state of a CAN bus system.