Feature:OOTDTY-Handy, fast and simple-For DTL, TTL and CMOS-High Frequescopic response-Instant indicationHeart rate set memory functionUsage:1. Connect the red terminal to the + terminal and the black tab to the power source terminal of the circuit under test. The supply voltage should not exceed 18V DC2. For TTL and DTL, set the top selection switch to the side marked "TIL", for CMOS, set the top selection switch to the side marked "CMOS", follow the probe pin to the test point. The LEDs will indicate its statuses:A) all high impedance LEDsB) red LED high state (1)C) green LED-low state (0)D) orange led hose ON - Pulse3. To detect and store a pulse or level transition, set the lower selector switch to the side labeled "pulse". Position the probe stem into the socket to be tested. The LEDs will indicate the base state. Then set the bottom selector switch on the page labeled "MEM", the orange led hose will light up when a pulse or level transition is detected. The direction of the pulse, compared to the original ground state, the state, determined by cabe. After use, reset the probe by turning the bottom selector switch back to the side labeled "PULSE"Package Included:1 * Probe