An interstellar beacon is a hypothetical omnidirectional antenna set up by an extraterrestrial civilization to broadcast its existence and/or other information to fellow technological races in the Galaxy or beyond. The presumption is that such a beacon would transmit some kind of repetitive message. However, the power required would be enormous. Whereas a beamed, unidirectional message from a race at a similar stage of technological development to our own would be easy to detect with conventional radio telescopes, even over distances of several hundred light-years, the same amount of power used to operate an interstellar beacon would result in a very feeble signal. Only an immense array of receivers, such as that proposed for Project Cyclops, would be capable of detecting the faint transmissions from interstellar beacons of Type I Kardashev civilizations outside the immediate solar neighborhood.