A frequency modulation oscillator is provided having three or more output frequencies corresponding to three or more possible input signals, the output frequency being a phase continuous frequency modulated signal with no discontinuities. For each desired output frequency, there is an input amplifier, responsive to an input binary signal, the output of that amplifier being summed with the outputs of the other amplifiers. For each input amplifier there is an active feedback network containing a delay element which will produce oscillation in the associated amplifier, the active feedback network from each amplifier being isolated from the other amplifiers and feedback networks.
A first stream of digits is converted to a second stream of alternating-current digits, each of the same amplitude and the same duration which may be different from the duration of the digits of the first stream, and which transmits at least the information in the first stream of digits at at least the same information rate. A number of alternating-current sources with different frequencies, the number at least as great as the greatest possible number of materially different groups of digits in the first stream, are connected one at a time to an output circuit in response to the first stream of digits to generate the second stream of alternating-current digits. The resultant wave may be limited at non-regenerative repeaters to remove amplitude noise, and may be regenerated in regenerative repeaters to remove substantially all noise and distortion.
A selectable oscillation circuit includes a first oscillation circuit, a second oscillation circuit, and a selector circuit. The selector circuit selectively switches on and off the first oscillation circuit and the second oscillation circuit, in accordance with the provision of a selector signal, to selectively switch between two communicating modes, with low-power consumption.
