A signal manipulation unit for use in a network element of a telecommunications network, comprising: a non-linear device for manipulating the signal; a digital pre-distortion unit adapted to generate a pre-distortion function and applying it to the signal before it reaches the non-linear device so as to compensate for nonlinearities in the device, the pre-distortion function generated using a set of stored parameters; an adaptation unit adapted to receive feedback from an output of the device and adapting the parameters in response to the received feedback; and a storage unit for storing the parameters used by the pre-distortion unit to generate the pre-distortion function; wherein the digital pre-distortion unit comprises: a function generator configured to generate a first pre-distortion function on the basis of a first set of parameters shortly before an initial discrete increase in power applied to the non-linear device: a signal distorter for applying the pre-distortion function to the signal; characterized in that the digital pre-distortion unit further comprises a clock configured to determine a predetermined time period after the initial power increase; in that the pre-distortion unit is configured so that, after the predetermined time period, the signal distorter stops generating the first pre-distortion function, and starts generating a second pre-distortion function generated on the basis of a second set of parameters, and shortly before the start of a subsequent discrete increase in power (2b, 2c) applied to the device, the signal distorter starts generating the first pre-distortion function on the basis of the first set of parameters, and in that the signal manipulation unit is configured to store the first set of parameters in the storage unit when the first pre-distortion function stops being generated after the initial power increase, so that the first set of parameters used to start generating the first pre-distortion function shortly before the subsequent power increase correspond to those at the end of the predetermined time period after the initial power increase. a non-linear device for manipulating the signal; a digital pre-distortion unit adapted to generate a pre-distortion function and applying it to the signal before it reaches the non-linear device so as to compensate for nonlinearities in the device, the pre-distortion function generated using a set of stored parameters; an adaptation unit adapted to receive feedback from an output of the device and adapting the parameters in response to the received feedback; and a storage unit for storing the parameters used by the pre-distortion unit to generate the pre-distortion function; wherein the digital pre-distortion unit comprises: a function generator configured to generate a first pre-distortion function on the basis of a first set of parameters shortly before an initial discrete increase in power applied to the non-linear device: a signal distorter for applying the pre-distortion function to the signal; a function generator configured to generate a first pre-distortion function on the basis of a first set of parameters shortly before an initial discrete increase in power applied to the non-linear device: a signal distorter for applying the pre-distortion function to the signal; a signal distorter for applying the pre-distortion function to the signal; characterized in that the digital pre-distortion unit further comprises a clock configured to determine a predetermined time period after the initial power increase; in that the pre-distortion unit is configured so that, after the predetermined time period, the signal distorter stops generating the first pre-distortion function, and starts generating a second pre-distortion function generated on the basis of a second set of parameters, and shortly before the start of a subsequent discrete increase in power (2b, 2c) applied to the device, the signal distorter starts generating the first pre-distortion function on the basis of the first set of parameters, and in that the signal manipulation unit is configured to store the first set of parameters in the storage unit when the first pre-distortion function stops being generated after the initial power increase, so that the first set of parameters used to start generating the first pre-distortion function shortly before the subsequent power increase correspond to those at the end of the predetermined time period after the initial power increase.