An apparatus comprising: a remote terminal unit, RTU, comprising: input/output (I/O) terminals configured to be coupled to at least one industrial control and automation field device ; one or more first I/O modules (204a-204n) comprising one or more first reconfigurable I/O channels (606a-606n) configured to be coupled to the I/O terminals, each first reconfigurable I/O channel configurable as an analog input, an analog input supporting digital communication, an analog output, an analog output supporting digital communication, a digital input, a digital output, and a pulse accumulator input; and at least one processing device configured to control a configuration of each of the one or more first reconfigurable I/O channels, characterized in that said RTU is further comprising: a first expansion board configured to be coupled to the one or more first I/O modules; a second expansion board configured to be coupled to one or more second I/O modules (210a-210n) comprising one or more second reconfigurable I/O channels (606a-606n), wherein the second expansion board is connected to the first expansion board; first and second electric paths (214a-214b) formed through the first expansion board and the second expansion board, wherein the first and second electric paths meet at a loop after a final expansion board to indicate a lack of any additional I/O modules or additional expansion boards. input/output (I/O) terminals configured to be coupled to at least one industrial control and automation field device ; one or more first I/O modules (204a-204n) comprising one or more first reconfigurable I/O channels (606a-606n) configured to be coupled to the I/O terminals, each first reconfigurable I/O channel configurable as an analog input, an analog input supporting digital communication, an analog output, an analog output supporting digital communication, a digital input, a digital output, and a pulse accumulator input; and at least one processing device configured to control a configuration of each of the one or more first reconfigurable I/O channels, characterized in that said RTU is further comprising: a first expansion board configured to be coupled to the one or more first I/O modules; a second expansion board configured to be coupled to one or more second I/O modules (210a-210n) comprising one or more second reconfigurable I/O channels (606a-606n), wherein the second expansion board is connected to the first expansion board; first and second electric paths (214a-214b) formed through the first expansion board and the second expansion board, wherein the first and second electric paths meet at a loop after a final expansion board to indicate a lack of any additional I/O modules or additional expansion boards. a first expansion board configured to be coupled to the one or more first I/O modules; a second expansion board configured to be coupled to one or more second I/O modules (210a-210n) comprising one or more second reconfigurable I/O channels (606a-606n), wherein the second expansion board is connected to the first expansion board; first and second electric paths (214a-214b) formed through the first expansion board and the second expansion board, wherein the first and second electric paths meet at a loop after a final expansion board to indicate a lack of any additional I/O modules or additional expansion boards. <EOS>