The DP-1 was designed to fill a long neglected need in the digital service industry. A completely automatic pulse generator in a pencil-sized probe, tailored for both the lab and field service. The DP-1 allows the user to conveniently pulse any family of digital circuits. By obtaining its power from the circuit it is testing, the DP-1 self adjusts the amplitude of its output pulse to the input requirements of the circuit under test. When the pulser tip is connected to the circuit node to be tested, the DP-1's "auto polarity sensing system'' selects the sink or source pulse required to activate the test point. Simply depress the push button once to produce a clean, bounce-free pulse. When the push button is held down for more than one second, the DP-1 produces a pulse train at a 100 pps rep rate. The DP-1 is capable of sinking or sourcing 100 mA or 60 TTL loads at a 1.5 microsecond pulse width. If a wider pulse is required simply move the TTL/ CMOS slide switch to the CMOS position to increase the pulse width to 10 microseconds. This allows reliable triggering of eVen the slowest CMOS devices at the lowest Vcc's. The DP-1 has a "Fail-Safe" feature, which permits an overvoltage condition up to 25 Volts. Further built-in protection will withstand a reverse Voltage to 50 Volts, and allows the DP-1 to pulse continuously into a short circuit. The DP-1 now gives the field service technician all the versatility of a lab quality pulse generator, without the need to set pulse levels or switch to complement the output pulse.