Abstract: To enable detection of a plurality of capsule ingestions, the ingestible capsules include a transmitter and processing hardware to generate and transmit the signals. Each ingestible capsule obtains a serial number for distinguishing between the ingestible capsules, and generates a signal indicating that the capsule has been ingested. The signal includes a series of pulses having a particular pulse space and indicating the serial number. Each ingestible capsule transmits the signal to a receiver via the transmitter, where each ingestible capsule is identified based on at least one of: the particular pulse space and the serial number for the ingestible capsule.