Bussmann series UL Type 4 24 Vac/ dc, 48 Vac/dc, 60 Vac/dc, 120 Vac/dc and 230 Vac/dc, two-pole, modular surge arresters feature local, easyID visual indication and remote contact signaling. The unique module locking system fixes the protection module to the base part. Modules can be easily replaced without tools by simply depressing the release buttons. Integrated mechanical coding between the base and protection module ensures against installing an incorrect replacement module.