1. In a disciplined frequency standard of the type having a variable frequency oscillator including a temperature dependent crystal resonator and an input circuit for driving the frequency of oscillation of the resonator in proportion to the magnitude of an electronic tuning signal applied to said input, and wherein said resonator is enclosed within an oven having an electrical heater for generating heat within the oven in response to the flow of electrical current through the heater, the improvement comprising a current sensing element coupled to said oven heater for producing an analog signal T proportional to the magnitude of current flowing through said sensing element, means for generating a parameter U proportional to the rate of change of frequency of the resonator with respect to the rate of change of temperature within said oven, and means for inputting an electronic tuning signal which includes as one of its components the product UT to the input circuit of said resonator circuit.