| 摘要 |
<p>A substantially fail-safe system for detection of flames, particularly flames in a fuel burner. A flame sensing means and amplifier that is responsive to the flicker frequency of a burning flame is coupled by a fail-safe type of circuit to a second safety type of amplifier. The second safety type of amplifier is a cyclic type of amplifier that requires a continuously cycling input signal in order for it to have an output indicating the existence of a flame at the flame sensing means. The failsafe coupling between the two amplifiers is a radiation emitting device and a radiation responsive device that are electrically isolated, and which are so selected and arranged that the system becomes inoperative upon a number of different types of failures.</p> |
