IPC Subgroup
H04M 3/16 with lock-out or secrecy provision in party-line systems
Introduced: September 1968
Last revised: January 2006
Full Title
Automatic or semi-automatic exchanges > with lock-out or secrecy provision in party-line systems
Classification Context
- Section:
- ELECTRICITY
- Class:
- ELECTRIC COMMUNICATION TECHNIQUE
- Subclass:
- TELEPHONIC COMMUNICATION