An active matrix electroluminescent display device has a shorting transistor (30) connected between the gate and drain of the drive transistor (22). Means (42) is provided for measuring a voltage on the data line (6). The shorting transistor (30) can be used to discharge the voltage on the gate of the drive transistor (22) until it switches off. By storing the resultant voltage on the data line (6) through an address transistor (16), the data line is used as one of the control/measurement lines for the threshold measurement.