Tamper protection for an automatic remote meter reading unit

#1. Technical Field

#The present invention relates to alarm systems and, more particularly, to an alarm system adapted for use in an energy management system.

#2. Description of the Prior Art

#The invention and its mode of operation will be more clearly understood from the following Detailed Description when read with the appended drawings in which:

#FIG. 1 is a block diagram illustrating the major functional components of the remote meter reading unit and their general interconnection with each other;

#FIGS. 2 and 3 depict a schematic diagram of an illustrative remote meter reading unit and disclose in particular detail the circuitry associated with the block diagram illustrated in FIG. 1; and

#Referring now to FIG. 1 of the drawings in accordance with the present invention, there is shown a block diagram of a tamper protection arrangement in an automatic remote meter reading unit. In the operation of the arrangement, signals reflecting a tamper from a water meter 100, a gas meter 200 and an electric meter 300 are provided to respective tamper circuits 101, 201, and 301 which transmit this information onto a communications controller 500. These tamper signals are provided whenever the meters are disconnected or the lines connected thereto tampered with. The class of tampers which can be detected includes open and shorted lines, and the series or parallel connection of additional resistance to the lines. These resistors would be connected with the intention of simulating the remote resistance by connecting this resistance, in either series or parallel, and then removing (opening or shorting) the remote resistance. Signals reflecting usage information from the meters are transmitted to respectively associated decoder circuits 150, 250, and 350 which, in turn, change this information to a form suitable for transmitting to the communications controller 500. To provide security for the communications controller 500, it also has an associated tamper circuit 501 that will be activated whenever access to its circuitry is obtained by an unauthorized person.

#In the event of a water meter tamper, the output of tamper circuit 101 which is normally at a logic one will go to a logic zero. This signal is coupled to one of the two inputs of AND gate 401. The second input to AND gate 401 has the output of the controller tamper circuit 501 which is also normally at a logic one. Changing the output of tamper circuit 101 to a logic zero also causes the output of AND gate 401 to go to a logic zero. This signal is coupled to the communications controller 500 and is interpreted as a water meter tamper.

#The gas meter tamper circuit 201 operates similar to the water meter tamper circuit 101. For a gas meter tamper, the output of tamper circuit 201 which is normally at a logic one goes to a logic zero. This signal is coupled to one of the two inputs of AND gate 402. The second input to this gate is the output of the controller tamper 501 which is also normally at a logic one. The output of tamper circuit 201 changing to a logic zero causes the output AND gate 402 to also go to a logic zero. This signal is coupled to the communications controller 500 and is interpreted as a gas meter tamper.