Resources Contact Us Home
Cordless telephone

Image Number 5 for United States Patent #4053717.

A cordless telephone including a Touch-tone signal generator module including ten buttons for initiating the generation of telephone switching signals representing ten numeric characters and two additional buttons; one of which is used for switching the cordless telephone into and out of a standby mode of operation in which a ring signal may be received and detected, and the other of which is used for providing off-hook and on-hook switching functions.The telephone lines are seized in response to a discrete control signal transmitted from the cordless telephone, which discrete control signal has a low freqency below an audio frequency band within which audio signals and switching signals transmitted from the cordless telephone are passed onto the telephone lines. These signals are transmitted by frequency modulation.The discrete control signal is summed with signals within the audio frequency band to provide a composite signal and an RF carrier signal is frequency modulated with the composite signal. Intermodulation between the discrete control signal and the audio and switching signals is prevented by providing a linear frequency deviation in response to amplitude variations in the composite signal.

  Recently Added Patents
Power generating apparatus of renewable energy type and method of attaching and detaching blade
Delta-sigma AD converter circuit and battery pack
Semiconductor thin film, thin film transistor, method for manufacturing same, and manufacturing equipment of semiconductor thin film
Method and apparatus for management and analysis of services in VoIP networks
Non-volatile memory cell containing a nano-rail electrode
High performance actuator motor
Eye therapy system
  Randomly Featured Patents
High pressure boundary seal
Parallel processing system having asynchronous SIMD processing and data parallel coding
Antenna apparatus
Self-propelled compost windrow turning and aerating machine and methods of operating the machine
Control apparatus to divide other communication apparatuses into multiple groups for slot allocated communication
Achromatic lens system including a diffraction lens
Position detector for a scanning device
Methods and apparatus for imaging volume data with shading
Thermal management technology for polarizing Xenon
Method and driver for programming phase change memory cell