Solenoid Design - Invert Mini
The solenoid used in the Empire markers (Mini, Axe, BT TM, etc) is a unique type of valve. It's so unique, in fact, that the developers in Taiwan have a couple special patents on it. This solenoid was first used in the XXX-I King Cobra marker, but the design was re-packaged and shrunk down when used with Invert Minis, then later other markers.
The interaction with surrounding air pressure is the other big difference with this valve, and this has to do with the magnetic fields created around it. As told by the animation, air pressure is pushing on the solenoid armature continuously while it rests idle. The design of the solenoid is such that the armature is magnetically suspended in the upward/idle position (in fact this can make solenoid reassembly difficult if the armature isn't seated to the correct position). When the solenoid becomes initially energized, the magnetic field created around it expands to encompass the entire solenoid coil instead of the stationary magnets inside. When this happens the armature pops to the downward position, and that entire internal chamber of the solenoid becomes pressurized.
After having been pressurized, the armature is effectively pushed and held in the down position due to the small exhaust port located on the underside of the solenoid. Because of this unbalancing, the solenoid no longer needs to be energized in order for the armature to be held in the downward position. As a result, the circuit board cuts power to the coil as long as the solenoid is supposed to be actuated. This is illustrated in the above animation by the solenoid coil becoming red only when the solenoid moves down.
When the solenoid needs to be reset, it receives a second pulse of energy to the coil which jolts the armature back into the upward position. As soon as the solenoid's bottom seat seal becomes unseated, the armature is "blown" upward by the act of pressure moving downward through it. This allows the solenoid to be popped upward where it will again suspend itself in that position by the stationary magnets inside the valve. This upward motion is also illustrated in the animation by the coil becoming energized a second time, except it moves upward during this energizing.
This is part of the process that makes the Invert solenoid reasonably well-performing in terms of battery power. It's only pressurized for a fraction of the total dwell time, when becoming actuated then again when de-actuating itself, so all of the time regular markers energize the solenoid during the "bolt moving forward" dwell time isn't present here, and that battery power is conserved for later. Additionally, due to the high impedance of the solenoid coil, a respectable circuit board driving the solenoid will pulse the signal, instead of delivering a full battery voltage to it.