... also don't overlook using the right size fuse for the smallest gauge wire you'll be using. If the Cat-5 uses 24AWG then you need to use a fuse size that's appropriate to keep that wire from melting the insulation and burning. Also the AWG gauge size in relation to length and current load will determine voltage drop.

Putting two wires of the same gauge together is roughly equal to one wire that is three gauges lower: Two 24-AWG wires is equal to one 21-AWG wire, and four 24-AWG wires would be equal to one 18-AWG wire.