Figure 2-42.  TOP bridle/pin configuration. Figure 2-43.  BOC pocket location. Figure 2-41.  Magnum pilot chute. The following describes the operation and installation  requirements of the CYPRES$^{®}$ model AA. Other designs,  such as the Vigil$^{®}$, are compatible with these installation  requirements. causing the pilot chute to release. Most older models use  a mechanical or pyrotechnic pin pulling technique. Newer  models use a pyrotechnic loop cutting design.  For many years, AADs were primarily used by the  military and student parachutists. The designs were bulky,  expensive, and, to a degree, inconsistent. The installations  themselves were cumbersome and awkward. In the early  1990s, a new generation of AADs became available. The  CYbernetic Parachute RElease System (CYPRES $^{®}$) uses  modern parachute release technology. It is small, reliable,  computer based, and uses a pyrotechnic loop cutter. It has  an auto-off feature that turns the unit off after 14 hours  of operation to conserve power. It also has the ability to  calibrate the unit for operation at altitudes other than the  calibrating ground level. Based on these concepts, other  companies have developed similar systems and as a result,  changed the approach to the design and use of AADs.  Today, a good many sport parachutists use an AAD and  some countries (rightly or wrongly), mandate their use by  all parachutists. The CYPRES$^{®}$ system is a barometrically controlled  microprocessor that activates a pyrotechnic cutter that cuts  the container locking loop. When calibrated to ground  level, the barometric sensor activates the unit firing the  cutter when the descending parachutist reaches an altitude  of approximately 750 feet above ground level (AGL) and  exceeds a rate of descent of 115 feet per second (fps). The CYPRES$^{®}$ consists of three parts:  Operation 1. Battery and processing unit  2. Control unit  3. Cutter  [Figure 2-45]  2-19