977142

Information

• Patent Grant
• 977142

• References
• Source

• Patent Number

  977,142

• Date Filed

  Not available

• Date Issued

  Tuesday, November 29, 1910
  114 years ago

• CPC

  • H04M3/2281 - Call monitoring
  • H04B1/582 - with automatic balancing

• US Classifications

  • 379 - Telephonic communications