Signalling applications surge protector - ESP SL Series. Ultra-slim low-resistance enhanced surge protector suitable for twisted pair signalling applications Very low let-through voltage between all lines Very low (1 ) in-line resistance High bandwidth Sturdy, flame retardant, polycarbonate housing Built-in DIN rail foot for easy installation 4-20 mA model (ESP SL30L/4-20) available with LED indication Also available with LED indication and isolated screen (ESP SL15L/I & ESP SL30L/I) Earthed through DIN rail foot or 4 sq mm earth terminal