The User$-$Programmable Model: This machine allows the car owner to enter a secret byte into a register. The user selects a byte using two hex keyboards, and presses an ENTERCODE pushbutton to store the code word. Now when the machine is used $"$in the field", the car owner enters a sequence using the same pushbutton arrangement as for the previous machine. When the sequence so entered matches the code word stored in the register, E goes HIGH. As with the Factory Preset Model, if more than $16$ bits are entered without the proper sequence being observed, the system shuts off $($until RESET is pressed$).$