I have a client with a large home ( 15K square feet, three floors) and the phone wiring is split up by floor with each floor being punched down into a 66 block specific to each floor. Line one keeps acting like a phone is off hook. There are four princess style phones and a Panasonic base unit with 8 cordless handsets. I was able to trouble shoot and isolate it to one floor where the on hook voltage would be about 39 volts while the other floors would be the standard 52. By the way, during trouble shooting there were no devices plugged into the phone outlets. By pulling extentions off of the 66 block one at a time until the voltage went from 39 back to 52, I was able to get some stability back into the system on line 1. Or, so I thought. The client called me the next day to say that the problem is back. I guess that the question is this: There are probably 50 different phone locations in the home that have no phone plugged in, can the amount of wire in the structured wiring system have a negative effect on the REN value to where I am having this trouble? Or is it simply one of the traditional phones or the Panasonic system not totally releasing the line after hanging up a call? I know phones are only two wires but this one is driving me nuts

The REN value is strictly the amount of AC current that the Telco supplies when there is an incoming call. When a phone is "On Hook", the voltage you are looking at is DC voltage. (About 48 VDC). When the phone rings, the Telco sends about 87 volts AC for each time the phone is ringing. If the phone company supplies a REN value of 8, for example, this means that there is enough current to ring the bells in 8 of the original AT&T/Western Electric phones. A modern phone doesn't have a "bell" and the current draw is probably half of one REN value. The 8 Panasonic cordless phones at your client's house uses less than one REN for all eight phones because the ringers are powered by the batteries in the phones. REN stands for Ringer Equivalent Number.

If all of the jacks are home run to the 66 blocks this should be fairly easy to troubleshoot.

You either have an intermittent short or ground fault in the wiring on one of the extensions, or you have a defective piece of telephone equipment. The amount of wire and number of jacks is not the issue.

Now you just have to do some trial and error.

Look for a wet jack.

I was once doing some phone work at a house where they were removing wallpaper, and when I tested after connecting a jack, everything was messed up. 90 minutes later, I realized that there was water in the phone jack at the bottom of the dripping wall.

Even if you have HUNDREDS of phone jacks, no DC current flows unless there is a short or resistance across the wires somewhere. You DID say the voltage was low with no phones plugged in, right?