9 persons skilled in the art will appreciate that variations may include using a different current magnitude e g greater than 1 a and or using a fixed polarity switching frequency to minimize complications of communicating with the mobile unit the user interface unit 7 may include various buttons and indicator lights on the front panel of the base unit 1 the interconnecting lead 8 may typically be embodied as a twin core cable to complete the current and voltage measurement circuits between the base unit 1 the mobile unit 9 and the item under test 16 the interconnecting lead 8 is a critical component of the split system design as it allows testing to be performed over a much wider range typically 200 m than traditional integrated solutions allow single joint the integrity signal detection unit 10 is in essence a filter tuned to pick out the signal impressed on the test lead by the base unit 1 it may be implemented as a band pass filter constructed from a combination of high pass and low pass filter circuits the output of this may be rectified and accumulated to provide a continuous signal to the microcontroller in the control module 13 the filtering circuits are preferably designed to provide a u2018 load u2019 on the.