Ryder Smart Logic 7 Way By-Pass Relay - TF2218/7E. This smart bypass fits virtually all cars, handles cars with standard or modulated circuitry (e.g. two functions in one bulb) and has a quiescent current of zero. Interface to the car is via signal wires from the relay. Interface to the trailer is via screw terminals. Ryder Smart Logic relays are quick and easy to fit, and very cost-effective. They bypass all the vehicle’s bulb-failure warning systems. They protect the vehicle against damage from the trailer wiring. They are compatible with LED trailer lights. They use smart logic to deal with cars that have one bulb handling two functions (e.g. brake lights and sidelights sharing the same bulbs). They have two fuses to protect the relay against short circuits in the trailer wiring. They are totally invisible to the car so the car does not detect them. The signal wires to the car’s rear lighting loom are protected so that only a milliamp can pass from the car to the relay and nothing can pass from the relay to the car. All the power to switch the relays and to operate the trailer lights comes directly from the vehicle’s fusebox or battery. They monitor the trailer flashers with both a built-in buzzer and a wire for a remote sounder or warning lamp. The relays are fully protected against electrical "spikes" and other electrical hazards. They are type-approved for EMC compliance.