LT1Poncho, I have never seen anything about relays in the numerous books I have about building layouts and the myriad number of model train magazines I have since 1989. The books I have include Greenberg's Model Railroading with Lionel Trains Volume II: An Advanced Layout by John Kouba, which I found extremely helpful.
If you remember, what specific relay did you buy, and where did you buy it, for your Lionel Double Signal Bridge.
Others can chime in and recommend a particular relay for this accessory, and where it can be purchased.
Arnold