Parallel ballasts use a single wire for connections to each end of a fluorescent tube. A shunted lampholder connects the lamp pins together. Generally instant start ballasts are wired in parallel.
2 and 3 Lamp Parallel Ballast Wiring
2 and 3 lamp parallel ballasts use blue wires for individual connections, and red wires for common connections. Black wire is for line voltage and white wire for neutral. A parallel ballast uses a single wire which connects from the ballast to each of the lamp terminals.