In this application, two 3-input NAND gates are used to create an active-low SR latch as shown in GUID-FBD1F883-1A75-4B75-B225-FFF6949531E3.html#APP1_SCHEM. The additional gate can be used for another application, or the inputs can be grounded and the channel left unused.

This device is used to drive the tamper indicator LED and provide one bit of data to the system controller. When the tamper switch outputs LOW, the output Q becomes HIGH. This output remains HIGH until the system controller addresses the event and sends a LOW signal to the R input which returns the Q output back to LOW.