Abstract: A two-wire process input-output (“IO”) transmitter powered by a two-wire process loop and configured as a single transmitter. The transmitter including a gateway module and at least one local IO module. The gateway module including a first circuit configured to wholly power the gateway module from the two-wire process loop, a second circuit configured to communicate via the two-wire process loop, and a third circuit configured to communicate with the at least one IO module via a local bus separated from the two-wire process loop. The at least one local IO module including a first circuit configured to wholly power the respective local IO module from the two-wire process loop, a second circuit to communicate at least with the gateway module via the local bus, and a third circuit configured to interface with at least one IO field device.