This is one of the oldest of ways to detect earthquakes and is already in available ready made in one form or another around the country. Here we use a couple of coat hangers, a magnet, wire and a ew electrical componants. You can make it as complex or as simple as you like and by using the alarm circuit below, you can create an automatic alarm that will require resetting. Again, this detection device is from an earthquake detector so it will double as on. If there wasn't an earthquake, then it might have been a high magnetic field that caused this device to trip. In ours we will use the coat hanger to creat the 'cradle' for the wire and magent. This is accomplished by bending the coat hanger as pictured in figures 1-3 below. Parts List: One Scrap Piece of Plywood (Anything bigger than One Foot Square Will Do.) One 9 Vdc Double-Pole-Double or Single Throw Relay. One 9 Vdc Lamp Two Coat Hangers One Ring Magnet (The Stronger The Better) 20 Guage Magnet Wire (Enamel Coated Wire) Staples (See Text) Hot Glue and Gun Jumper Wires (Optional) One Buzzer (Optional) The first piece (Frame 130) is secured onto the plywood base using constuction or telephone staples. Use enough to attach well enough to keep the hanger from sliding around or sagging. I used a ring magnet that was rather expensive as far as magnets go. It measures approximately 1.3 inches in diameter 3/8" in depth and 1/8" in thickness and is made from Alco 5. Experimenting with different magnets is encouraged. Some shapes and materials may work as well or better than the one I used but, first try what you have laying around. Frame 137 shows the alarm circuit which will latch and stay on untill you reset by pussing the switch. This can be used on most of the above detectors easily. Shown here is a simple device using a relay which has two sets of "on" contacts in order to latch the relay one there is a short from the detector. An optional buzzer can be installed and is your preferrence on type. The lamp could also be optional if you prefer an audible alarm over a visible one. An audible alarm you need not be watching the detectors all the time.