A wrong number generator is a prank device which can be attached to a phone line, scrambling the tones so that when someone dials a number, the wrong number goes through. As one might imagine, constantly dialing a wrong number would be extremely irritating for most people, and one could consider a wrong number generator to be a rather malicious prank, depending on the sense of humor of the victim. These devices are sold at prank stores and sometimes through sites which cater to the geek community.
As a general rule, a wrong number generator randomizes the calls which will go through correctly, dialing wrong numbers around three quarters of the tine and allowing the other quarter of the calls to go through without difficulty. The wrong number generator will also always transmit calls to emergency services, although it is a very good idea to confirm that the wrong number generator has been programmed for a particular region's wrong numbers. In some cases, the device can also be programmed to allow certain phone calls to always go through.
This device only impacts outgoing calls, so the effect is totally on the person who uses the phone line, along with the unwitting victims on the other end who are called by accident. In the case of someone who uses the phone at odd hours, a wrong number generator could be considered doubly cruel, because it is not only irritating to the caller, but also to someone who gets out of bed at odd hours of the morning to answer calls which turn out to be wrong numbers.
There are several ways to install wrong number generators. Most come with a number of options, allowing people to jack them directly into the phone box or to conceal them in the phone jack behind the wall in addition to plugging them into the phone. If the victim is not very technology savvy, a wrong number generator may torment them until the pranker takes mercy and removes it or reveals the joke, or until he or she calls the phone company for help.
There is some caution involved in installing a wrong number generator. In some areas, it is not legal to work in a phone junction box unless you are an employee of the phone company, for example, so you could be subject to prosecution. The victim could also decide that the wrong number generator constitutes harassment, and he or she could file charges. You may want to consider these issues before installing a wrong number generator.