(I am rewriting this review 8/20/15 having used this incredible product for 2-/12 years. I would give it a 10.) I might mention I am also a retired electrical engineer with a background in radio telemetry. So consider my tips-tricks and insights valid.~~~~~~~~~~I am using this Loc8tor to keep track of my cat(s) outdoors. I live in a rural area. They normally don't stray far, but have their hiding spots and occasionally are pre occupied chasing chipmunks and doing whatever it is rural cats do. Living in a rural area, I have very little extraneous radio noise from cell phones, wifi, etc. common in residential-suburban areas. So thats a consideration.My acreage( 40) is heavily wooded so that has been part of my usage learning curve.My former (now deceased) kitty "Fuzz", was a real cruiser. Never once was I unable to find her even though it sometimes required an effort. She was "semi trained" to respond to the collar chirping and return home. When a link is made by radio, the collar fob will chirp. Eventually animals learn this has a meaning.My current cat "Lulu" was obtained as a 12 week old kitten, kept inside through the winter and a focused effort made on basic training. I am not going to write a treatise on how to train a cat except to say they are totally trainable with association, repetition, rewards, patience and kindness.Lu was trained to come to her name and also to the fob chirp using kitty treats. All done indoors over the winter, well before being introduced to outside. She predictably comes like a rocket and always gets her kitty treats when she comes in. Lou is a GEM!What I am suggesting is the Loc8tor is not only a great device for locating an animal, but also can be used to call one in. I E Pavlov's Cat.~~~~~~~~~Study the instructions. Experiment with this off your pet so you understand how it works before you trust it. There is a learning curve but it isn't rocket science. You can tell distance, direction and whether or not an animal is moving by interpreting the LEDs on the handheld transceiver. It doesn't take long- Its quite intuitive.~~~~~~~~~Batteries; I wouldn't rely on the batteries that come with the device. Age being unknown. Batteries can be bought (cheap) on Amazon. They are inexpensive and common. This device will work only as well the the batteries being fresh. When depleted, range will drop off substantially until either the FOB or handheld transceiver quits. Battery type and installation is covered in detail in the instructions.The fobs use a pair of small button cells in series. The transceiver uses a 3v coin cell. The locator used 2-3x daily is good for 8-12 weeks between battery changes. If you have a digital meter, replace the coin cell and/or the two button cells (tested in series) at 2.75 volts. @ <-2.5 volts. the fob/ transceiver will quit working.A couple days ago, I couldn't get a signal lock- ZIPPO NADA ZILCH- and thought Lulu had run off? Long story made short, a recently replaced "new" battery in the fob was found defective and stone dead. Quick replacement and back in business. If you are having issues, check or replace the batteries before thinking a fob is faulty. They either work great, not so great, or not at all. Its easier to tell when transceiver battery is down, dim LEDS.Waterproofing: The fobs are somewhat "water resistant" but hardly water proof. Hanging one from a collar won't cut it. I cut a piece of electrical tape 1/4" wide and go all around the seam on the fob. The fob then goes into a protective sleeve on the collar, secured at both ends with twist ties (nipped off and bent flush to the collar). (see photo )I use these: inexpensive and come in a 4 pack. Unless the fobs are water protected, they won't last long outside. There are better molded silicone rubber ones available.http://www.amazon.com/gp/product/B007W6MVUM?psc=1&redirect=true&ref_=oh_aui_detailpage_o07_s00~~~~~~~~~~~Range: What's realistic? Loc8tor suggests 400' line of sight (meaning no trees, buildings, etc. in the way) I would say this is realistic in a rural area somewhat free of extraneous "radio noise". It would be typically less in residential areas with fences, buildings etc. as barriers. My cat skulking through dense ferns will diminish the link distance by 20-40%, but since I know the haunts, I know where to look when I get a few intermittent blips. The higher the fob is in the air without obstructions, the stronger and farther the link potential. But there are other considerations, as well.A few useful tips:Tip #1: Hold the transceiver card horizontal-flat (or at a slight upward incline) by a bottom corner. This way your hand will not block outgoing or incoming radio signals. Dampening obstructions are obstructions, including your hand. The further the fob from the transceiver, the more dampening effect an obstruction has.Tip #2: The Loc8tor comes with two fobs. I use them both on the same collar, keyed as #1 and #2, right and left facing. (These weigh virtually nothing so kitty will hardly notice). Reason#1: Depending on kitty's orientation to the handheld transceiver, I may get nothing (or a weak signal) from the away facing fob and a good response to the facing fob. With a single away facing fob and a poor link, it could be misinterpreted that kitty is farther than she actually is: Kitty's neck can also be a signal obstruction. Two fobs you have an option and backup. Reason #2: Switching back and forth between two fobs, extends battery life of each with half as much use time between battery changes.Tip #3: To see what might happen, I punched holes in the collar every 1/2" and threaded through a 6" piece of highly flexible, small gauge, stranded wire, essentially acting as a booster antenna built into the collar. Line of sight tests with that modification jumped range from 400' to 800-1000' feet. Doubled. I believe I can get 1/4 mile (1300') in cooler weather with leaves down. Thats pretty impressive for a 3volt milliwatt signal.Loc8tor really is state of the art micro electronic engineering. I AM IMPRESSED! I don't makes this comment lightly. Three seasons of use and I have ALWAYS been able to locate and call in my critters- easily and without worry. Well engineered and works better than advertised. Awesome product with lots of other applications, too.