For designs that incorporate the SEP device on the line side of the transformer, Littelfuse strongly recommends the Enhanced TeleLink® fuse be chosen. This fuse was specifically designed to protect the SEP technology devices. While the fuses look identical, the difference between the Enhanced TeleLink® and the standard TeleLink® fuses is that the Enhanced version is assured to open in five minutes during the 30 minute 2.2A power cross test. This means the fuse will open cleanly before the SEP device achieves dangerous temperatures. Both the standard TeleLink® and the Enhanced TeleLink® fuses are surge tolerant so nuisance opening is eliminated.