Figure 14. Circuit for ballast control with combined displacement and rate-of-ascent switches.
Figure 15 is a theoretical height-time curve, showing when ballast would be dropped using such a control and the resulting balloon behavior. During ascent the pressure pen is kept off the commutator bar until Point 1 where it falls onto the low-altitude conducting segment. (The shelf has been set so that the pen will fall onto the low-altitude segment in order that a ballast signal will be received for a short period of time, indicating that the system is working properly. The balloon rises and ballast flows until the pressure pen reaches Point 2, the beginning of the region where both switches in series control the ballast. As long as the balloon continues to rise, no flow occurs. Should the maximum altitude be above the control level, no ballast will flow until the balloon descends to that point. Then, with both controls operating, ballast will flow only on the descending and floating portions of the flight below control level. A second course is illustrated, wherein the rate-switch has failed. There the balloon descends to Point 2 and oscillates about this level, as a result