Some OEM sources/head-units have a test circuit that monitors the presence of a low-impedance load to enable audio outputs. When you connect this type of head-unit to the high-level inputs of an Audison bit processor, which has a high impedance load, audio outputs are silenced. By inserting the USS 4 between the source and the processor / amplifier, these problems are definitively solved. If there is a need to generate a remote signal to control the amplifier turn on/off, it is necessary to power the USS4, providing the additional feature of the possibility to delay the signal from 1 to 8 seconds, so as to avoid annoying “bumps” upon ignition. In countries where the legislation on electromagnetic compatibility is not mandatory under ECE / UN Regulation no. 10/5