Resources Contact Us Home
Telephone intercommunication system providing common access to a communication line

Image Number 4 for United States Patent #3931479.

A private telephone intercommunication system including facilities for connecting the system to a telephone central office. Common supervisory means are provided to control access to a line from each station.

  Recently Added Patents
Reducing energy and increasing speed by an instruction substituting subsequent instructions with specific function instruction
Distributed mobile access point acquisition
Polymers derived from benzobis(silolothiophene) and their use as organic semiconductors
Interconnecting virtual domains
Lens barrel and imaging device
Lightning-protective explosion-preventive fastener
Semiconductor device with an amorphous semi-insulating layer, temperature sensor, and method of manufacturing a semiconductor device
  Randomly Featured Patents
Tape cartridge drive belt having a low ratio of static to dynamic friction
Method of upgrading gravel and/or dirt roads and a composite road resulting therefrom
Cleaning device with releasable, disposable head
Sign system
Imaging lens, optical apparatus equipped therewith and method for manufacturing the imaging lens
Reference potential generator and a semiconductor memory device having the same
Propylene polymer, copolymers and elastomer
Line current differential protective relaying method and relay for in-zone tapped transformers
Bidding in online auctions
Method and an arrangement for generating a ringing signal