In this application, two 4-input NAND gates are used to create an active-low SR latch as shown in Figure 9-1. Unused inputs can be tied together or to V_CC

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.