A communication apparatus operates with a supply voltage of a power and transmits a sensor value with a digital communication method using consecutive frames. In the communication apparatus, a data source unit is configured to generate a frame using a data of a sensor value processed by a signal processing unit. A switching unit is configured to perform a signal switching to permit a transmission circuit to perform a re-transmission of re-transmitting a signal including the sensor value stored in a memory in response to a restoration of the power after an instantaneous power interruption. A frame monitoring unit is configured to monitor a status of a frame transmission and determine a frame at the occurrence of the instantaneous power interruption. The sensor value to be re-transmitted is determined based on information of the frame determined by the frame monitoring unit at the occurrence of the instantaneous power interruption.