Circuit Powered Logic Probe with Audio Beeper, TTL and CMOS, 20MHz Max FrequencyCircuit powered logic probe designed for troubleshooting fast logic circuits Tests TTL and CMOS logic families Minimum pulse width detection of 30 nanoseconds and a maximum input frequency of 20MHz Two sound audio beeper and LED indicators for Hi and Low Switch selectable pulse detection or pulse memory function This circuit powered beeping logic probe is designed for troubleshooting fast logic circuits. It features TTL and CMOS compatibility, switch