The equipment was designed to test insulated cables. While testing the insulated core, it passes through the transducer and in this way it reaches an electric field of (0… 20 kilowatt) ball-chain high voltage. As the conductor part of the core is reticulated in the zero electric field in case of insulation error the high voltage closes towards ground and error voltage starts up in the 20kw- error detecting transformer. It is detected by an electric circuit and it switches off the high voltage immediately and sends an error alert. The error alert including flashlight, acoustic warning and contact signals are feasible to stop the production line. The error alert is continuous until acknowledgement! After the ackowledgement the error alert ceases and the testing voltage reverts automatically.