Supervisory control system

Claim 2

A supervisory control system for use between a control station 10 and a remote station 11 connected by a pair of transmission lines 12, 13 carrying an a.c. signal, comprising: first rectifying means 42, 43 having an output terminal 45, said first rectifying means being connected across said transmission lines 12, 13 at said remote station 11 for generating a rectified signal at said output terminal 45; an electromechanical device 44 at said remote station connected between one of said transmission lines 12 and said output terminal 45; second rectifying means 17 in said one transmission line 12 at said control station 10 for blocking positive-going signals from said remote station coming in on said one line 12; means 20 for rendering said second rectifying means unblocking; condition responsive switch means 47, 48 at said remote station 11 for selectively connecting said output terminal 45 to earth ground; and means at said control station 10, including an earth ground connection 78 responsive to the selective connection and disconnection of said output terminal 45 to earth grouNd at the said remote station 11 for indicating the state of said condition responsive switch means 47, 48.

Claim 3

The supervisory control system of claim 1 wherein said indicating means includes a relay coil, back-to-back diodes connected in series across said transmission lines at said control station, means for connecting the mid-point between said back-to-back diodes to one end of said relay coil and means for connecting the other end of said relay coil to earth ground.

Claim 4

The supervisory control system of claim 1 wherein said first rectifying means includes a pair of face-to-face diodes connected in series across said transmission lines at said remote station, the mid-point between said two diodes constituting said output terminal.

Claim 5

The supervisory control system of claim 3 wherein said condition responsive switch means includes a diode and a switch connected in series between said output terminal and earth ground.

Claim 6

The supervisory control system of claim 4 wherein said switch is opened responsively to a predetermined alarm condition.

Claim 7

The supervisory control system of claim 4 further including means at said remote station for sensing the magnitude of a predetermined condition and for closing said switch means for a time period over a predetermined time interval proportional to the magnitude of said predetermined condition, and wherein said indicating means includes means at said control station for indicating said time period.

Claim 8

The supervisory control system of claim 6 wherein said predetermined condition is fluid flow rate.

Claim 9

The supervisory control system of claim 1 and further including means responsive to current flow in said transmission lines for indicating the presence of said current flow.

Claim 10

The supervisory control system of claim 1 and further including an isolation transformer having a secondary winding connected across said transmission lines at said control station, and means for matching the impedance of said isolation transformer to the impedance of said transmission lines.

Claim 11

The supervisory control system of claim 9 further including back-to-back diodes connected across said secondary winding and a relay coil connected between the mid-point between said back-to-back diodes and earth ground.

Claim 14

A supervisory control system for use between a control station and a remote station connected by a pair of transmission lines carrying an a.c. signal, comprising: first rectifying means having an output terminal, said first rectifying means being connected across said transmission lines at said remote station for generating a half-wave rectified signal at said output terminal; an electromechanical device at said remote station connected between one of said transmission lines and said output terminal; second rectifying means in said one transmission line at said control station for blocking positive-going signals from said remote station coming in on said one line; means for rendering said second rectifying means unblocking; condition responsive switch means at said remote station for selectively connecting said output terminal to earth ground; and means at said control station for indicating the state of said condition responsive switch means, said first rectifying means including a pair of face-to-face diodes connected in series across said transmission lines at said remote station, the mid-point between said two diodes constituting said output terminal, and further including means connected between said output terminal and the other of said transmission lines for providing a conducting path around the diode therebetween in response to the energization of said electromagnetic device with the rendering of said second rectifying means unblocking.

Claim 15

A supervisory control system for use between a control station and a remote station connected by a pair of transmission lines carrying an a.c. signal, comprising: first rectifying means having an output terminal, said first rectifying means being connected across said transmission lines at said remote station for generating a half-wave rectified signal at said output terminal; an electromechanical device at said remote station connected between one of said transmission lines and said output terminal; second rectifying means in said one transmission line at said control station for blocking positive-going signals from said remote station coming in on said one line; means for rendering said second rectifying means unblocking; condition responsive switch means at said remote station for selectively connecting said output terminal to earth ground; and means at said control station for indicating the state of said condition responsive switch means, said first rectifying means including a pair of face-to-face diodes connected in series across said transmission lines at said remote station, the mid-point between said two diodes constituting said output terminal, and further including means connected between said output terminal and the other of said transmission lines for providing a conducting path around the diode therebetween in response to the energization of said electromagnetic device with the rendering of said second rectifying means unblocking.