In SLIC SIDACtor devices there is a diode integrated into the design. This is perfect for SLIC circuits where positive voltages are damaging and must be eliminated. SLIC is an acronym for the (subscriber line interface circuit). This is the device that creates the telephone line, including the voice signal, dial tone, busy signal, ringing and a host of other functions. One terminal, marked (G) in the diagram, is connected to ground while the other is connected to either the tip or ring line. Two of these protection devices are needed for every SLIC port, one for tip and one for ring.