Below is a list of High Voltage Coils manufacturers from Concord, California. High voltage coils are electrical coils that use a voltage higher than what is generally accepted as safe. High voltage refers to a currency that is potentially dangerous due to the possibility of sparks in the air and a possible electric shock to those in contact with the coil or in close proximity. Another way in which a high voltage is determined is if there are any insulation requirements specific to the voltage.