The oil pressure method is old and archaic. The better method is mine...
The module reads the speeds pulses from the electronic speedometer. When speeds decrease to under 6.68 mph, the coil energizes the kickdown solenoid which opens the valley in the valve body for 1st gear start. Of course, adding an in-line factory dash switch in series defeats the circuit and you have 2nd gear start (back to normal).
Anyone else interested, please give me a ring or send me an e-mail.