The small square relays made by Bosch and several other manufacturers are very handy to use, and they have the added advantage of being available at any parts store, not obsolete and scarce like the 40-year-old ones from junkyards. There are two basic types, 4-pin relays that just have two normally-open contacts and two coil terminals, and the 5-pin types that have both normally-open and normally-closed positions for the load contacts. Many of them have wiring diagrams molded right into the relay housing.
An added advantage to the little Bosch relay is the fact that connections can be made with regular female blade-type connectors, and the plastic case doesn't have to be grounded.
Jerry
