If none of the instructions are acknowledged, the program turns all outputs on and stops the program. The program uses an all on instruction to better illustrate the condition. There are often times when the program does not have any outputs on and appears to be working, but is actually off doing something else. The Tuttle1 PLC uses a very simple for of logic to get the required outputs given a set of inputs. The micro-controller requires a large amount of programming to achieve the outputs that are achievable using Tuttle1 logic.
Several alterations are available to the program to customize the logic for advanced programmers.
Relay interfacing can be available right on the card itself. The inputs are a little more difficult and if possible require a five volt supply.