3560670

Information

• Patent Grant
• 3560670

• References
• Source

• Patent Number

  3,560,670

• Date Filed

  Not available

• Date Issued

  Tuesday, February 2, 1971
  54 years ago

• CPC

  • H04Q1/26 - for signalling trouble in unoccupied sub-exchanges
  • H04B17/408 - using successive loop-backs

• US Classifications

  • 455 - Telecommunications