http://www.chesshouse.com/v/news/2007/03/dgt-easy-digital-chess-clock.html
http://www.chess.com/eq/chess+clocks/chronos-digital-chess-clock-ii---touch-switch How to use, and manual listed on the page.
Unfortunately, I don't have any personal experience with it.
I do have this one and like it.
I have the smaller version, since it fits in the bag with my pieces I carry with me. It's easily the best clock I've ever used. Setting it is intuitive after you've played with it for 5 minutes, and I really enjoy the minimalist design. Only three buttons. And I have the touch version, so really there is only one moving part on it; so I expect this clock to last for the next 30 years. The clock itself has really sturdy construction, it feels as though I could throw it off a bridge and it would still work.
Everything about it is configurable. You can change the frequency of the beep (or turn it off). You can make it have an LED, or not. Or just flash an LED on your turn. You can have it halt clocks at the end of a game, or keep ticking and let your opponent go into negatives. You can have n second delays, or add time at the start of a turn. Configure it to give bonus time after a certain number of turns.
I also think it has a mode where it will give you a random Chess 960 position -- however I haven't tried to do that yet.
I am looking at buying a Chronos chess clock for over the board play. I was planning on getting the larger size since it is probably the only chess clock I'll ever need and ten bucks isn't going to make much of a difference when you are spending $100 already. Having used an opponent's clock, I think I would prefer push botton to touch. I am interested in hearing any experience you might have either way, though. I have looked at wholesalechess.com, uscf sales, and here at chess.com and there seems to be several models of just the Chronos Digital Chess Clock push button style. There is the Chronos Digital Chess Clock and the Chronos Digital Chess Clock II. The one at uscf has different dimensions from the one sold from wholesalechess.com. Any help or suggestions would be appreciated.