Transponder system including an oscillator/ripple counter controlling a fixed gray code logic network in circuit with a driver/gate circuit for generating "red-alert" end condition digital signals in a storage tank gauging system

Claim 1

Transponder network for generating a "red-alert" digital code upon (i) occurrence of an overflow condition within a storage tank under survey and (ii) receipt of a square wave interrogation signal from a transmitter/receiver of a tank gauging system located at a central station remote from said storage tank but electrically connected to said transponder network through an INTERROGATION, a MARK and a SPACE line of said tank gauging system, comprising: (A) I/O network for receiving said interrogation signal including voltage divider means for generating a microcircuit drive voltage for a period concident with the pulse width of said interrogation signal; (B) an oscillator/ripple counter formed essentially of MSI's connected to said I/O network and including at an input, a power-on-reset network for generating a reset pulse for said oscillator/ripple counter, said oscillator/ripple counter generating, in response to said reset pulse, sets of square wave pulses of differing repetition rates and pulse widths; (C) an encoding means and NAND gate means connected to each other and to (B) responding to selected sets of said square wave pulses to generate a synthetic digital code at microcircuit signal levels at an output means of said gate means; (D) drive means including switching transistor means having one or more inputs connected to said NAND gate means of (C), and one or more output means connected to said MARK and SPACE lines through said I/O of (A), said drive means being controllable as a function of said synthetic digital code to drive said MARK and SPACE lines between tank gauging operating potentials for generating said "red-alert" digital code of interest at said central station whereby said overflow condition within said storage tank can be indicated.