Abstract: The invention concerns an apparatus and technique for detecting the voltage of A.C. high voltage lines. A radar wave is transmitted towards the high voltage lines and is reflected to a detector when the AC voltage drops to threshold level. Reflection continues until the AC voltage cycles to the threshold level on it second half of the cycle. A time interval is calculated for radar reflection and non-reflection, and a ratio thereof is calculated by a microprocessor which generates a display indicating the voltage carried by the AC lines in accordance with the time interval ratio.