Supervisory control system

Claim 2

A supervisory control system for operating a plurality of field points comprising a central control station including transmittter means for transmitting messages each formed of bits corresponding to an address of one of said field points, said messages being transmitted in a biphase code with each bit having a bit time with a transition near the center thereof, and said transmitter means including scanning means for forming messages to automatically sequentially address said field points; a plurality of remote stations each including receiver means for receiving said messages, a group of said field points and decoder means connected with said recEiver means for addressing said field points, said receiver means including means for generating bit signals in accordance with bit transitions of said messages, window generator means responsive to each bit signal to generate a window pulse after a predetermined time less than one bit time, each window pulse having a width to span the center of the next bit time, and gating means receiving said window pulses and said bit signals and passing said bit signals to said decoder means only when said bit signals coincide with said window pulses; and transmission means for coupling said central control station with said remote stations.

Claim 3

A supervisory control system as recited in claim 1 wherein said transmission means is a shielded, twisted pair of wires coupled with said transmitter means and said receiver means to provide differential transmission and common mode rejection of noise.

Claim 4

A supervisory control system as recited in claim 2 wherein said transmitter means includes line driver means, capacitance means coupling said line driver means to said pair of wires and encoder and inhibit means for supplying said messages to said line driver means for transmission via said pair of wires and for inhibiting said line driver means to discharge said capacitance means and effectively disconnect said line driver means from said pair of wires.

Claim 5

A supervisory control system as recited in claim 1 wherein each of said remote stations includes transmitter means for transmitting answer messages from field points addressed by said messages from said central control station, said address messages from said remote station transmitter means being transmitted in a biphase code with each bit having a bit time with a transition near the center thereof, and said central control station includes receiver means for receiving said answer messages from said remote stations and for generating bit signals in accordance with bit transitions thereof, window generator means responsive to each bit signal to generate a window pulse after a predetermined time less than one bit time, each window pulse having a width to span the center of the next bit time, and gating means receiving said window pulses and said bit signals and passing said bit signals only when said bit signals coincide with said window pulses.

Claim 6

A supervisory control system as recited in claim 4 wherein said transmitter means at each of said stations provides an inhibit signal when a message is being transmitted, said inhibit signal being supplied to said receiver means at said station to inhibit operation thereof.

Claim 7

A supervisory control system as recited in claim 4 wherein each of said messages includes a synchronizing code followed by a message body and said receiver means at each of said stations includes code comparison means responsive to said synchronizing code to pass said message body.

Claim 8

A supervisory control system as recited in claim 6 wherein said code comparison means includes a synchronization counter for counting said bit signals and sequence gating means responsive to the output of said synchronization counter to sequentially receive bits only corresponding to said synchronizing code.

Claim 9

A supervisory control system as recited in claim 7 wherein said synchronizing code has a first bit of a first predetermined state and a second bit of a second predetermined state and said code comparison means is responsive to a received bit of said first predetermined state to trigger said synchronization counter, and said sequence gating means is responsive to triggering of said synchronization counter to be conditioned to receive a next bit of said second predetermined state.

Claim 10

A supervisory control system as recited in claim 8 wherein said gating means receiving said window pulses and said bit signals provides a pulse to reset said synchronization counter if no bit signal is received during a window pulse.

Claim 11

A supervisory control system as recited in claim 9 wherein said window generator means includeS window counter means, clock pulse means for supplying clock pulses to said window counter means, means for supplying said bit signals to said window counter means to cause said window counting means to count said clock pulses, means responsive to said window counter means for supplying a window pulse to said gating means when said window counter means is between first and second predetermined counts, and means responsive to said gating means to supply a pulse to reset said window counter means when a bit signal coincides with a window pulse.

Claim 12

A supervisory control system as recited in claim 6 wherein said message body is formed of first and second identical words and said receiver means at each of said stations includes a data register for storing said first word after said synchronizing code is received and comparison gating means for receiving said second word bit by bit and comparing said second word with said first word from said data register bit by bit.

Claim 13

A supervisory control system as recited in claim 4 wherein said field points at said remote stations include analog and status points, and said transmitter means at said remote stations includes means for forming bits in said answer messages corresponding to an analog value at said analog points and a condition at said status points.

Claim 14

A supervisory control system as recited in claim 1 wherein said window generator means includes window counter means, clock pulse means for supplying clock pulses to said window counter means, means responsive to said bit signals to cause said window counter means to count said clock pulses, means responsive to said window counter means for supplying a window pulse to said gating means when said window counter means is between first and second predetermined counts, and means responsive to said gating means to supply a pulse to reset said window counter means when a bit signal coincides with a window pulse.

Claim 15

A supervisory control system comprising a central control station; a plurality of remote stations; and transmission line means connecting said central control station with said remote stations, said central control station and said remote stations each including transmitter means for transmitting messages via said transmission line means in a biphase code with each bit having a bit time with a transition near the center thereof, and said central control station and said remote stations each including receiver means for receiving messages from said transmitter means via said transmission line means, said receiver means including means for generating bit signals in accordance with bit transitions of said transmitted messages, window counter means, clock pulse means for supplying clock pulses to said window counter means, means responsive to said bit signals to cause said window counting means to count said clock pulses, means responsive to said window counter means for providing window pulses when said window counter means is between first and second predetermined counts, said first predetermined count being reached after a period of time less than one bit time and said second predetermined count being reached after a period of time greater than one bit time such that each of said window pulses spans the center of a next successive bit time, and gating means receiving said window pulses and said bit signals to pass said bit signals only when said bit signals coincide with said window pulses.

Claim 16

A supervisory control system comprising a central control station; a plurality of remote stations; and transmission line means connecting said central control station with said remote stations, said central control station and said remote stations each including transmitter means for transmitting messages via said transmission line means in a biphase code with each bit having a bit time with a transition near the center thereof, and said central control station and said remote stations each including receiver means for receiving messages from said transmitter means via said transmission line means, said receiver means including means for generating bit signals in accordance with bit transitions of said transmitted messages, window counter means, clock pulse means for supplying clock pulses to said window counter means, means responsive to said bit signals to cause said window counting means to count said clock pulses, means responsive to said window counter means for providing window pulses when said window counter means is between first and second predetermined counts, said first predetermined count being reached after a period of time less than one bit time and said second predetermined count being reached after a period of time greater than one bit time such that each of said window pulses spans the center of a next successive bit time, and gating means receiving said window pulses and said bit signals to pass said bit signals only when said bit signals coincide with said window pulses.

Claim 17

A supervisory control system as recited in claim 14 wherein said receiver means includes means responsive to said gating means to reset said window counter means when a bit signal is received in coincidence with a window pulse.

Claim 18

A supervisory control system as recited in claim 15 wherein said transmission line means includes a shielded, twisted pair of wires and said transmitter means includes a line driver capacitively coupled with said pair of wires and encoder and inhibit means for operating said line driver to effectively disconnect said liNe driver from said pair of wires when no messages are being transmitted.

Claim 19

A supervisory control system comprising a central control station; a plurality of remote stations; and transmission line means connecting said central control station with said remote stations, said central control station and said remote stations each including transmitter means for transmitting messages via said transmission line means in a biphase code with each bit having a bit time with a transition between first and second levels near the center thereof, and said central control station and said remote stations each including receiver means for receiving messages from said transmitter means via said transmission line means, said receiver means including means for generating pulse signals in accordance with transitions of each bit of said transmitted messages and level signals in accordance with said first and second levels of each bit of said transmitted messages, data means, means for supplying said level signals to said data means, and timing means responsive to said pulse signals to supply data pulses to said data means to control passing of said level signals into said data means whereby the bits of said transmitted messages are self-clocked into said data means.

Claim 20

A supervisory control system comprising a central control station; a plurality of remote stations; and transmission line means connecting said central control station with said remote stations, said central control station and said remote stations each including transmitter means for transmitting messages via said transmission line means in a biphase code with each bit having a bit time with a transition between first and second levels near the center thereof, and said central control station and said remote stations each including receiver means for receiving messages from said transmitter means via said transmission line means, said receiver means including means for generating pulse signals in accordance with transitions of each bit of said transmitted messages and level signals in accordance with said first and second levels of each bit of said transmitted messages, data means, means for supplying said level signals to said data means, and timing means responsive to said pulse signals to supply data pulses to said data means to control passing of said level signals into said data means whereby the bits of said transmitted messages are self-clocked into said data means.

Claim 21

A supervisory control system as recited in claim 17 wherein said timing means includes window generator means responsive to each pulse signal to generate a window pulse after a predetermined period of time less than one bit time but greater than one-half bit time, each window pulse having a width to span the center of the next bit time, and gating means receiving said window pulses and said pulse signals to supply said data pulses to said data means only when said pulse signals coincide with said window pulses.

Claim 22

A supervisory control system as recited in claim 18 wherein said messages each include first and and identical words, said data means includes a data register for storing said level signals corresponding to said first word and comparison means receiving said level signals corresponding to said second word, said level signals from said data register corresponding to said first word and said data pulses to compare said first and second words bit by bit in timed relation with said data pulses.

Claim 23

A supervisory control system as recited in claim 19 wherein each of said first and second words is formed of a predetermined number of bits and said data means includes a data counter counting said data pulses and having an output for enabling said comparison means when said predetermined number of data pulses have been counted.

Claim 24

A supervisory control system as recited in claim 17 wherein said transmission line means is a shielded twisted pair of wires, and each of said receiver means includes high impedance, high pass filter means coupled with said pair of wires whereby a large number of central and remote stations can be connected via said pair of wires without substantially degrading the messages.

Claim 25

A supervisory control system as recited in claim 21 wherein each of said transmitter means includes line driver means for selectively connecting and disconnecting said transmitter means with said pair of wires.

Claim 26

A supervisory control system as recited in claim 22 wherein each of said transmitter means includes capacitance means coupling said line driver means to said pair of wires and encoder and inhibit means for supplying said messages to said line driver means for transmission via siad pair of wires and for inhibiting said line driver means to discharge said capacitance means and effectively disconnect said line driver means from said pair of wires.