It can also be used to test fibre optic connections or cables, as can be seen somewhat hidden in the data sheet. The two silver connectors are intended for this purpose. The additional device is intended on the one hand for testing LAN cables and on the other hand the blue nöpel is intended for non-contact voltage (NCV), i.e. for cable search. There is an analogue and a digital version of NCV. Yes Unfortunately there is no manual on the net. It is not a high-end device for the price, but rudimentary tests and cable searches work well. You can also determine the length of a cable break to estimate where the cable is broken. I have not yet tested fibre optics.