Wiring Hookup on Aftermarket Cruise Control Unit

I am rewiring ann old street rod that has an aftermarket cruise control in it.  All of the hookup wires were markeed except one.  There is a wire to the coil, ground, power, and the cold side of the brake light circut.  Can anybody give me a clue as to where the last wire goes?   Its red if that helps.  There is no separate speed sensor that I can see so I assume that the coil hookup provides that function.  Thanks in advance for your help.Dave Mahle

Usually here's the common hookup from the cruises I am familiar with: Black - Ground Brown - Ignition/Accessory Power Blue or Gray - Tachometer Wire Gray or Blue - Speed Sense Wire Purple - Cold Side Of Brake Red - Hot Side Of Brake Good luck..If thats no good maybe you could tell us what type of cruise it is and somebody might know more.