Jerry--
There's lots of info in Chapter 2, Signaling, of 'Reference Manual for
Telecommunications Engineering, 2d ed.,' edited by Roger L. Freeman,
Wiley-Interscience, 1994, ISBN 0-471-57960-2. Have fun!
Outside of a dog, a book is man's best friend.
Inside of a dog it's too dark to read.
---Groucho