Abstract: An ARINC Specification 429 transmitter provided with self test capability. A dual transmitter (10) converts parallel data provided from an external source through a bidirectional data bus (12) to a serial data format corresponding to Aeronautical Radio Incorporated (ARINC) Specification 429. The dual transmitter includes two first-in-first-out (FIFO) storage buffers (20a, 20b), which may be used separately by each transmitter, or alternatively may be daisy chained to provide 128 words of buffered storage for one of the transmitters. One of two different fault detection tests or modes is enabled upon hardware or software reset of the dual transmitter. In a scan test mode, the dual transmitter transmits ARINC data while generating a signature value corresponding to the data for comparison to an expected signature value generated by an external microporcessor or computer, to detect errors in the data input to the device or a fault in the internal circuitry of the dual transmitter.