3649771

Information

• Patent Grant
• 3649771

• References
• Source

• Patent Number

  3,649,771

• Date Filed

  Not available

• Date Issued

  Tuesday, March 14, 1972
  52 years ago

• CPC

  • H04Q1/4535 - with an additional signal transmitted for voice protection

• US Classifications

  • 340 - Communications: electrical
  • 379 - Telephonic communications