This so-called shield assembly forms a type of bow, which is hydraulically pressed against the rock and tensioned. This is enabled by a master cylinder between runner and cap, as well as additional cylinders which extend the cap or press it back against the rock. This shield is also advanced by cylinders when the machines operating under its protection have removed another section of the seam and the shield must follow the coal.

These are located together with the control electronics in a shared rectangular solenoid housing of around 40 millimeters by 80 millimeters. This has the advantage that only one connector is required, and simplifies handling for the user. Finally, around six to eight twin solenoids are used per shield. With around 150 shields per longwall, this gives a total of 800 to 1200 twin solenoids that must be supplied with electric power.

The main hazard in coal mining is still caused by the fact that the coal releases combustible gases, which can explode in so-called fire damp. The ignition of very fine coal dust has also cost many lives. Since it only requires the emission of a small spark, all electrical equipment must be designed to ensure that no sparking occurs (intrinsically safe equipment).

The control electronics of the twin solenoids is particularly clever, as the system is designed to save energy: while the armature is initially attracted with a rated current of 100 milliamps and a force of ten newtons, it reduces the current to around 50 percent of the initial value in a time-controlled manner when the armature has reached the pole. It thus utilizes the specified effect that the magnetic force, on account of the air gap between armature and pole, increases to approx. 40 newtons at rated current in the stroke end position, and can also reliably hold the hydraulic valve in the end position with 20 newtons at reduced current.