Alarm and utility meter reading system employing telephone lines

• US 3,922,490 A
• Filed: 06/18/1973
• Issued: 11/25/1975
• Est. Priority Date: 06/18/1973
• Status: Expired due to Term

• Current Assignee: Charles D. Pettis
• Original Assignee: Charles D. Pettis
• Inventors: Pettis, Charles D.
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Chin, Tommy P.
• Application Number:
  US05/370,975
• Time in Patent Office: 890 Days
• Field of Search: 340/149,180,177VA,177VZ 179/2A,2R,5R 324/62R,65R,115
• US Class Current: 379/106.03
• CPC Class Codes: H04M 11/002 with telemetering systems telemetering in general G08C
• CPC Class Codes: H04M 11/04 with alarm systems, e.g. fire, police or burglar alarm systems

Abstract

Disclosed is a system for utilizing existing telephone subscriber lines during ON hook conditions for low level direct current signalling. The system employs basically a stepped resistance element connected across the subscriber line with remote switches for short circuiting discrete resistance steps. Employing binary encoded resistance steps a large number of signalling conditions may be transmitted with the stepped resistance element acting as an extremely simple encoder. Utility meters may be easily monitored. The resistance element and sensor switches are connected in simple logical arrangements whereby many identifiable signals may be sent including fail safe and test information.

Claims

1. A signalling system for use in conjunction with a telephone subscriber set, a pair of line conductors forming a subscriber loop and a central location for concentrating a number of subscriber lines comprising a resistance element including a plurality of series connected discrete resistances;

said resistance element connected across said line conductors without any active or reactive elements in D.C. conduction relationship with said subscriber loop and in parallel with said telephone subscriber set;

at least one normally open switch connected across one of said discrete resistances;

said switch being closable to produce a step change in D.C. resistance of the subscriber loop indicative of a signalling condition;

said resistance element having a resistance with said switch closed greater than the minimum value interfering with normal central office switching or voice conversation.

2. The combination in accordance with claim 1 wherein said resistance element includes at least two discrete resistances and individual normally open switches connected across each of said discrete resistances, said discrete resistances having different values whereby the D.C. loop resistance changes a different amount with closure of one or the other of said switches.

3. The combination in accordance with claim 2 wherein said discrete resistances have different values differing by a factor n where n is an integer.

4. The combination in accordance with claim 2 wherein the switch associated with the larger of said discrete resistances is operable by the most significant signalling event.

5. The combination in accordance with claim 2 including multiple means connected to a plurality of subscriber loops for sequentially sampling the D.C. loop resistance of each of said subscriber loops, means for connecting the loop resistance monitored into digital signal format and means for displaying a discrete change of loop resistance as a signal condition.

6. The combination in accordance with claim 2 including adjustable resistance means in series with said resistance element for adjusting the total loop D.C. resistance to a predetermined value.

7. The combination in accordance with claim 5 wherein said central location includes battery means for applying D.C. to said subscriber loop, said means for converting the loop resistance into digital signal format is connected to the same battery as said subscriber loop.

8. The combination in accordance with claim 2 including addItional switch means connected across a plurality of said discrete resistances whereby the closure of said additional switch means produces a greater change in resistance than the operation of any one of said individual switches whereby a higher priority signal of greater detectability may be produced.

9. The combination in accordance with claim 2 wherein the said resistances differ in value by different values whereby the closure of any individual one of said switch means or any combination thereof produces a different change in D.C. loop resistance.

10. A telephone subscriber installation comprising in combination a pair of line conductors, a telephone subset including a pair of hook switches for connecting said subset across said line conductors, a ringer connected across said line conductors, a signalling subset without any active or reactive elements connected across said line conductors, said signalling subset comprising a resistive element comprising a plurality of series connected resistances having a total value between 5,000 and 70,000 ohms, individual switch means connected across respective resistances, said individual switch means being operative to change the resistance of the subscriber installation when said hook switches are open, said resistances having different values whereby the operation of different switches is identifiable and detectable by the magnitude in any change in loop current through the line conductors when connected to a D.C. power source.

11. The combination in accordance with claim 10 wherein said switches are operable to denote different alarm conditions.

12. The combination in accordance with claim 10 where said resistances are each of different values, each differing from the next lower value by a factor n where n is an integer of each other whereby the operation of any single or any combination of switches produces a discrete resistance change.

13. The combination in accordance with claim 10 wherein said signalling subset includes an adjustable series resistance connected in series with said resistive element for adjusting the nominal D.C. resistance through said subscriber station.

14. The combination in accordance with claim 10 including an additional switch means for selectively shunting a plurality of said resistances to produce a discrete change in resistance greater than the resistance change produced by the operation of any of the other of said individual switch means.

15. Apparatus for sensing and signalling an indication of utility consumption as function of operation of such meter comprising, switch means coupled to said meter for producing a switch closing and opening for a predetermined consumption as registered by said meter, a resistance element including at least two discrete resistances connected in series, said switch means connected to shunt one of said discrete resistances upon the closing thereof, a pair of line conductors connectable to a central utility data recording center;

said resistance element connected across said line conductors without any active or reactive elements whereby said resistance element determines in part the loop resistance as seen by a central utility data recording center and said switch means producing a detectable change in loop resistance with each predetermined utility comsumption.

16. The combination in accordance with claim 15 wherein said line conductors constitute a telephone line and said resistance element is connected in parallel with the ringer of a telephone set connected to said line conductors.

17. Apparatus for sensing and signalling an indication of utility consumption as function of operation of such meter comprising, switch means coupled to said meter for producing a switch closing and opening for a predetermined consumption as registered by said meter, a resistance element including at least two discrete resistances connecTed in series, said switch means connected to shunt one of said discrete resistances upon the closing thereof, a pair of line conductors connectable to a central utility data recording center;

said resistance element connected across said line conductors whereby said resistance element determines in part the loop resistance as seen by a central utility data recording center, said switch means producing a detectable change in loop resistance with each predetermined utility consumption;

wherein said apparatus includes an enclosure securable to the face of a utility meter with said switch in position to be actuated by a magnet in said meter, said switch means including a second switch, a second resistance element selectively shunted by said second switch, said second resistance element connected in series with said first mentioned resistance element, said second switch being magnetically operated and positioned to respond to magnetic fields originating from sources other than said utility meter magnet to operate and produce a discrete change in the resistance across said apparatus.

18. The combination in accordance with claim 17 wherein said second resistance element is different in value from said first resistance whereby the operation of said first or second switches are distinguishable.

19. Apparatus for sensing and signalling an indication of utility consumption as function of operation of such meter comprising, switch means coupled to said meter for producing a switch closing and opening for a predetermined consumption as registered by said meter, a resistance element including at least two discrete resistances connected in series, said switch means connected to shunt one of said discrete resistances upon the closing thereof, a pair of line conductors connectable to a central utility data recording center;

said resistance element connected across said line conductors whereby said resistance element determines in part the loop resistance as seen by a central utility data recording center;

said switch means producing a detectable change in loop resistance with each predetermined utility consumption;

wherein said switch means comprises a magnetically actuated switch and said meter includes a magnet coupled for movement with a consumption monitoring element of said meter to produce sequential opening and closing of said switch with predetermined quality of utility consumption.

20. The combination in accordance with claim 18 wherein said monitoring element of such meter is a rotatable indicator and said magnet is mounted thereon for rotation cyclically into switch opening and closing relation with said switch.