Mallinckrodt & Mallinckrodt
Telemetry alarm system
 A telemetry system adapted to monitor earth slope stability comprises a minimum of one earth slope stability sensor connected with timing means, which, upon the sensing of slope instability, initiates transmission of a timed signal of a predetermined carrier frequency, and a superimposed tone frequency, by an associated transmitter. A receiver picks up the transmitted signal along with stray signals and feeds all such received signals to a decoder which produces corresponding pulses. The pulses from the decoder enter a time gate circuit, which determines if the time durations of the respective pulses fall within predetermined maximum and minimum limits and which also produces an output signal if a pulse is within such limits. The output signal is used for alarm purposes. It is ordinarily desired to simultaneously monitor several sites of possible earth slope instability. For this purpose, several sets of stability monitors, timers, and transmitters are provided. Each transmitter is adapted to superimpose an additional tone frequency signal upon the transmitted signal, none of which additional tone signals are alike. The received signals are also sent to a series of identifiers, each of which has an alarm associated therewith and is adapted to produce an output if a predetermined additional tone frequency signal is present. If an output is generated by both the identifier and the time gate circuit, alarm activating means is energized to give an alarm that indicates in which area the slope instability has occurred. 
Kennecott Copper Corporation
E
E21F
inventional
Michael K. Dale J.
McCarter Green