Ok Bill. I mentioned the transmitter as it allows easier installation, and, sometimes a better choice of mounting location. I went wireless so I would have the freedom to mount the sensors in the best location rather than having cable length dictate where I could put the sensors.
Telephone cord will work but any splice points must be waterproof, especially if you use the modular plugs. Davis includes wire housings with their extension cables, but I found they leaked. Better to have one long wire run then try to splice pieces together.