The 1953A is a systems counter with a wide array ot options allowing you to select just the capability you need. The 1953A can provide a variety of measurements: frequency, frequency ratio, period, period averaging, time interval, and gated totalizing. Trigger level controls allow selection of a preset level (OV dc), or adjustment to suit conditions. DMM output jacks and LED status indicators help the user to set the trigger levels properly. Signal conditioning switches permit the operator to select positive or negative slope trigger, ac or dc coupling, and X1 or X10 attenuation. A marker output is provided for use with an oscilloscope for accurate determination of trigger points. The GPIB/IEEE-488* interface option (1953A- 15) allows full programming of function, range, and signal conditioning, including trigger levels. Data output includes 9 digits of display information, decimal point, and exponent. Front panel lockout is provided. TTL level parallel remote programming (1953A-12) is also available. (Both these options are built into the unit and must be ordered at the time of purchase.)