DLC compact surge protective devices (SPDs) are designed to protect terminal equipment connected to industrial buses, telecommunication lines or signalling applications from the effects of lightning and transient overvoltages. These SPDs are installed on symmetrical DIN rail, often within customer panels. DLC SPDs protect 1-pair applications and have a non-pluggable (monobloc) enclosure. Many types are available to cover most applications. D2 types are best suited to floating applications, D3 types offer full-mode protection across all lines with D3G types additionally providing specific protection for the signalling ground wire.