The present invention relates to devices, systems and methods to maintain self-expanding stents in a compressed form during delivery to and positioning at a treatment site. The system comprises an on-line separator device in the vacuum sewer piping and a first pump means and a second pump means connected in parallel with the on-line separator device. A controller detects activation of each data entry key on the keypad by a user, and also detects the number of times the data entry key is activated. The level shifter circuit enables voltage level shifting a logic signal from a high to a low operating voltage, or from a low to a high operating voltage. Related systems are also provided. The invention also concerns a lighting system implementing this method, an array of such electrical systems and a method for detecting one or a plurality of malfunctions of such a lighting system.