12 Volt Lead Acid Battery Monitor: This simple circuit makes it possible to monitor the charging process to a higher level.

50 MHz Frequency Counter, Voltage Meter & SWR / PWR Indicator:

Audio Level Indicator: Audio Amplifier output relay delay

Audio Volume Indicator: (PDF) uses an XS40 Board and XStend Board to display the volume of an audio input on a barograph LED.

Battery Charge Indicator:

Battery Chargers indicates Rate of Charge: 05/25/95 EDN-Design Ideas /  A single LED indicates whether the battery Chargers s delivering a trickle charge or a fast charge, circuit designed to charge2-14 cells

Battery condition indicator12v :

Battery Equal Charge Indicator:

Battery Monitor Emulates Auto Dashboard: 07/03/97 EDN-Design Ideas

Blown Fuse Indicator: