A pressure control device, preferably for use in a control system of an automatic transmission of a motor vehicle, is shown as having a solenoid motor assembly the armature of which, through a cooperating servo orifice, is effective for varying the magnitude of pressure of a fluid medium acting upon...http://www.google.com.au/patents/US5217047?utm_source=gb-gplus-sharePatent US5217047 - Solenoid operated pressure regulating valve
