Sets the transducer of signal edfsignal ("AgAgCl cup electrodes", etc.).
edf_set_transducer(edf_handle, edfsignal, transducer)
: integer containing file handle of the opened bdf/edf-file
: Minimum value is 1
: string containing the transducer text of the signal edfsignal.
This function is optional for every signal and can be called only after opening a file in writemode and before the first sample write action.