I'm looking to get some help understanding the tachometer out specifications for an MSD 6AL ignition control unit. It specifies that "The Tach Output wire produces a 12 voltage square wave signal with a 22.5° duty cycle." I'm fine with the fact that its a 12 volt square wave, but I'm a little lost on the 22.5° duty cycle. I think it is referring to a duty cycle that spans 22.5 degrees of one revolution of the distributor, but want to make sure 22.5° isn't a different way of specifying something like 22.5% duty cycle? If so, then can some one provide insight as to what they expect the base frequency to be? I've got an email in to MSD as well for their help, but as its the weekend I'd like to get an answer sooner than Monday.