The 5300A Measurement System Mainframe unit provides the system power, reference frequency, display, counting logic and timing control required for plug-ins (sold separately). Features include: 6-digit dot matrix display, overflow indicator, standard timebase, external timebase input and BCD output as a standard rear panel output. The crystal frequency is 10 MHz with a typical stability of 2 parts in 106. Oscillator output is 10MHz, approximately 1 Vrms at rear panel BNC, 100-ohm source impedance.