Yes, Telco wiring can be used between Enable-IT Ethernet Extender units.
Any wiring used has to be as contiguous as possible with no other connections like a Telco punch down block or extensions. Telco punch down blocks add interference and can introduce other electrical paths that will degrade performance or interfere with the data signal communications.
The 1-pair or wire used should be terminated directly into a RJ-45 blank LAN head and inserted into the Interlink port of each Enable-IT Ethernet Extender unit. If using Telco wire over 3,000ft, add a piece of twisted pair wiring to each end of the Telco wire connection between the Ethernet Extenders as this will boost the signal strength and increase your performance.
Ethernet Extenders communicate on very high frequencies and therefore by nature these frequencies bleed over into surrounding wires. We highly recommend you do not place multiple extender kits or use on lines that have other high frequency signals (such as Digital PBX or other telecommunication circuits from a carrier) on the same wire or surrounding wires. Always uses separate runs(wiring) for Ethernet extender kits as to maximize the throughput. You may be successful in isolating different pairs in a 25,50 or 100 pair Telco bundle, however this is up to your own trial and error.
Issues to be aware of:
1) Be aware of other high speed communications ruining over the same Telco wiring bundle of 25, 50 or 100 pair as this communication may bleed out to surrounding wires and cause interference/noise on your 1-pair of wiring between the Ethernet Extenders. If you suspect this is an issue try a different pair to isolate your communications.
2) Twisted pair wire (CAT5, CAT6, CAT3) will always give better performance than telephone wire.