The Hewlett-Packard Mode! 5386A is a frequency counter that makes frequency and period measurements. The HP 5386A has a Frequency range of 10 Hz to 3 GHz. The counter is a microcomputer based instrument with a data bus port for remote operation through HP-IB. Channel "A” has a female BNC type connector. Channel "B" has a female N type connector. To the left of the "A” channel input connector is a control that allows you to set the trigger level of Channel A. A 100 kHz low pass filter can be toggled in or or out of the Channel A signal path. Measurement display and mode annunciators are shown on a 12-character alphanumeric liquid crystal display (LCD). Frequency and period measurement displayed in engineering format, with three alpha caracters used to designate units, e.g., MHz. The display will also give you brief messages and diagnostic prompts. The HP 5386A is designed so it may either be rack mounted or stacked. A 10 MHz reference oscillator output is included. The connector for the 10 MHz output may also be used as an external 10 MHz reference oscillator input connection. Option 004 is an ovenized oscillator that provides a high stability time base giving substantially higher accuracy over variations in time and temperature. HP-IB is the Hewlett-Packard interface Bus for remote control of the counters by computers and controllers, it is a standard feature in the instrument,