A method of compensating for the temperature related frequency drift of an oscillator, the method comprising: comparing an external reference frequency signal and an output signal of the oscillator, using a control loop, to derive oscillator compensation data over a range of operating temperatures; storing the oscillator compensation data in a first table; for a given operating temperature, using the first table to obtain a corresponding oscillator compensation value and applying that value to provide compensation for the temperature related frequency drift, characterized by defining, for the range of operating temperatures, a series of temperature slots each sub-divided into a series of temperature bins; and the step of using the external reference frequency signal to derive oscillator compensation data over the range of operating temperatures comprising: a) measuring an operating temperature and comparing the frequency of the external reference frequency signal with the frequency of the output signal of the oscillator to determine oscillator compensation values for respective temperatures as the operating temperature varies; b) accumulating the determined oscillator compensation values in corresponding temperature bins of a second table, including, for each value, adding the value to a sum for the bin stored in the second table and incrementing a count for the bin; c) at spaced intervals in time, using the values accumulated in the temperature bins of the second table and the respective counts of the bins to determine, for each of one or more slots in the first table, parameters of a linear relationship relating temperature to compensation value across the slot, defined by a linear equation including said parameters. comparing an external reference frequency signal and an output signal of the oscillator, using a control loop, to derive oscillator compensation data over a range of operating temperatures; storing the oscillator compensation data in a first table; for a given operating temperature, using the first table to obtain a corresponding oscillator compensation value and applying that value to provide compensation for the temperature related frequency drift, defining, for the range of operating temperatures, a series of temperature slots each sub-divided into a series of temperature bins; and the step of using the external reference frequency signal to derive oscillator compensation data over the range of operating temperatures comprising: a) measuring an operating temperature and comparing the frequency of the external reference frequency signal with the frequency of the output signal of the oscillator to determine oscillator compensation values for respective temperatures as the operating temperature varies; b) accumulating the determined oscillator compensation values in corresponding temperature bins of a second table, including, for each value, adding the value to a sum for the bin stored in the second table and incrementing a count for the bin; c) at spaced intervals in time, using the values accumulated in the temperature bins of the second table and the respective counts of the bins to determine, for each of one or more slots in the first table, parameters of a linear relationship relating temperature to compensation value across the slot, defined by a linear equation including said parameters. a) measuring an operating temperature and comparing the frequency of the external reference frequency signal with the frequency of the output signal of the oscillator to determine oscillator compensation values for respective temperatures as the operating temperature varies; b) accumulating the determined oscillator compensation values in corresponding temperature bins of a second table, including, for each value, adding the value to a sum for the bin stored in the second table and incrementing a count for the bin; c) at spaced intervals in time, using the values accumulated in the temperature bins of the second table and the respective counts of the bins to determine, for each of one or more slots in the first table, parameters of a linear relationship relating temperature to compensation value across the slot, defined by a linear equation including said parameters.