The Telos 100 is a great box, but probably more than you need.
Let's review what a phone hybrid does. The telephone line is a single circuit, with both send and receive audio on it. The "send" audio is from your board in the studio. the "receive" audio is the caller, wherever he may be. The hybrid seperates those into two circuits, one for send, the other for receive.
The receive audio, ideally, would be ONLY the receive audio. Even though it came from a circuit that contained both send and receive, the send audio is "nulled" out, so that theoretically only the receive audio is left.
The null circuit works by balancing the audio in one place against the audio in another place. When they match perfectly, you get a perfect null. But the reality is that they never match perfectly, so the null isn't perfect, and you end up with a little bit of your send audio on the receive audio pot on the board.
When this is really bad, your mic seems to be hotter through the caller pot than the caller himself is. The function of this hybid is the main reason you constantly hear talk show hosts telling their caller to speak up. Because even the best phone hybrids can only do so much.
The biggest problem in obtaining a consistent null in a radio station is that the phone lines are part of the null circuit, and the impedance of each phone line differs from the next. While a good sounding hybrid can be built really cheaply, it has to be adjusted for the deepest null on one phone line only. The other lines may not sound so good!
Thus, the "auto nulling" phone hybrids were invented, of which the Telos 100 is one of the best ones ever made. When you pick up the line, the hybrid gives a burst of noise down the phone line and an onboard computer nulls out the hybrid to that line. It all happens in less than a second, and you get the best null on that line that you can get.
But if you only have 1 phone line, that box may be overkill. Yes, it has some built in compression and EQ. But really... the big thing you are paying for with that is the auto null feature.
If money were an issue, I would look for an old Gentner SPH 3, 4, or 5 on Ebay. Or I'd consider the Broadcast Tools TT1 for $129.
http://www.bswusa.com/proditem.asp?item=TT1
Or a step up from that is the JK Audio Inline Patch for $239...
http://www.bswusa.com/proditem.asp?item=INLINEPATCH
Keep in mind you will have to manually null those units to your phone line. It's a matter of sending a tone down the line and adjusting a pot for minimum bleed-through.
But it beats spending a lot of money you don't need to spend.
