Train Horn Relay Wiring - With four visibly marked blade terminals, this relay was designed for horn installation but can also be used with compressors, power trunks and many other 12V applications.. Zone Tech 12V Dual Trumpet Horn - Premium Quality Classic Black Super Loud Powerful Train Sound Shiny Dual Car Van Truck Boat Air Horn The brand new Zone Tech 12V Dual Trumpet Horn kit emits a Loud Powerful tuned train sound. The Great Bellowing Sound catches everyone's attention and is heard all over. The two durable trumpets can produce sound as loud as 115DB.. We update the Railway Technical Website from time to time. While we try to get everything in place correctly, there are bound to be some minor glitches..