CDA signals are all hand made from brass in our own work shop. No plastic is used. All of CDA signals feature low current LED’s and are prewired with the correct resistor so that they can be connected to any 12v DC or 15v AC outlet. Thus eliminating the chances of blowouts and giving long life. #’s 144, 145, 146 and 147 feature two coloured LED’s which change colour with the reversing of power.