SD-144A is a LCD self-powered digital hour meter, with powerful microprocessor and memory techniques. It keeps track of running time for all types of engine. The operation of hour meter can be triggered by either spark plug signal of engine or transducer of engine shaft or motor reel and magnetic signal. This is useful for maintenance and warranty applications for any type of engine-powered machinery. The unit is powered by an internal lithium battery. No external power connection is required.