The Stanford Research SR625 Frequency Counter consists of a frequency counter (SR620), a high-accuracy rubidium timebase (PRS10), and a 2 GHz input prescaler. The combination of the SR620 and the prescaler allows direct frequency measurements up to 2 GHz with twelve digits of resolution in a 100 s measurement. The rubidium timebase ensures excellent short-term stablity (<2 10-11 Allan variance (1 s)) and long-term drift (<5 10-11/month). The SR625's warmup time is less than ten minutes making it ideal for field applications. An additional back-panel output provides a rubidium stablized 10 MHz signal which can be used to drive other test equipment (e.g., synthesizers or spectrum analyzers). The standard GPIB and RS-232 interfaces allow for complete control and data acquisition from any laboratory computer. The SR625's performance makes it the standard for remote applications or laboratory calibration.