The 5174 provides two major functions, serving as a precision Voltage Controlled oscillator board and a variable frequency source board. These features can be use together or independently. As a variable frequency source, the 5174 provides a high-resolution variable clock source that is based upon a reference clock supplied by the ECM carrier. The FPGA on the carrier can use the Local Oscillator/PLL, the VCO, or the various inputs as the reference clock source. As a voltage controlled oscillator A 20MHz VCO controlled by an on-board DAC provides a pullable frequency output to the ECM carrier. A temperature sensor is provides readings to compensate for frequency change versus temperature effects.