| From 1870 there were various attempts to build | | | | interference between a radio transmitter and |
| a machine that could detect metal or ore rich | | | | receiver was caused by ore deposits and by |
| rocks as this would be a great mining tool. All | | | | passing a piece of metal between them the signal |
| these attempts ended up with a clumsy power | | | | was altered. He developed the first metal |
| hungry device that was extremely unreliable and | | | | detector that worked on this principle in his shed |
| practically useless. No major breakthroughs were | | | | and started producing them for buyers. A patent |
| made until in 1931 Gerhard Fisher a scientist | | | | was given to him for this device in 1937 and he |
| working in Los Angeles on aircraft directional | | | | went on to create what is today Fisher |
| equipment made an observation that prompted | | | | Detectors. |
| him to make metal detectors. He noticed that | | | | |