×

Tamper protection for an automatic remote meter reading unit

  • US 4,357,601 A
  • Filed: 09/02/1980
  • Issued: 11/02/1982
  • Est. Priority Date: 09/02/1980
  • Status: Expired due to Term
First Claim
Patent Images

1. A tamper protection arrangement comprising a resistance element (132), a resistance sensing circuit (101) for detecting changes in the value of the resistance element and providing an alarm signal in respect to the changes in the value of the resistance element characterized in thatthe resistance sensing circuit comprises a first transistor (109) connected directly to the resistance element and a second transistor also connected directly to the resistance element, the first transistor being turned on responsive to an increase in the value of the resistance element and the second transistor being turned on responsive to a decrease in the value of the resistance element.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×