This part of IEC 60444 applies to the measurements of drive level dependence (DLD) of quartz crystal units. Two test methods (A and C) and one referential method (B) are described. Method A , based on the À-network according to IEC 60444-1, can be used in the complete frequency range covered by this part of IEC 60444. Reference Method B , based on the À- network or reflection method according to IEC 60444-1, IEC 60444-5 or IEC 60444-8 can be used in the complete frequency range covered by this part of IEC 60444. Method C , an oscillator method, is suitable for measurements of fundamental mode crystal units in larger quantities with fixed conditions. NOTE Measurement methods specified in this document is not only applicable to AT-cut but also applicable to other crystal cuts and vibration modes, such as doubly rotated cuts (IT,SC) and to tuning fork crystal units (by using a high impedance test fixture).