Frequency shifted modulated carrier protective relaying system with amplitude modulated voice communication

Claim 2

A relaying system comprising a fault sensing network having a first output and a second output, a transmitter, said transmitter including circuitry to provide an output signal at first and second frequencies, said transmitter further including circuitry to amplitude modulate said output signal at both said first and second frequencies, means connecting said transmitter to said fault sensing network whereby said first output will cause said transmitter to transmit said signal at a minimum power magnitude and whereby said second output will cause said transmitter to transmit said signal at a maximum power magnitude, circuit means connected to said transmitter and effective to cause said transmitter to modulate said signal as a function of its output frequency, said circuit means actuating said transmitter to transmit said signal at a power magnitude above said minimum magnitude and to limit the modulation of said signal thereby to prevent the power magnitude of said signal from reaching a value less than said minimum power magnitude.

Claim 3

The combination Of claim 1 in which said circuit means attenuates all frequencies below a desired minimum frequency whereby to attenuate side band frequencies of said signal.

Claim 4

The combination of claim 2 in which the magnitude of said attenuated side band frequencies is at least equal to the magnitude of the difference in frequency between said first frequency and said second frequency.

Claim 5

The combination of claim 3 in which there is provided a source of ringing frequency connected to said transmitter and effective to modulate said signal, a receiver adapted to demodulate said amplitude modulated portion of said signal to provide an output signal derived from said signal portion, an audio frequency sensitive device connected to said circuit means and effective to control the output frequency of said circuit means, a call device, an audio frequency output device, and circuit means connecting said receiver to said call device and to said audio frequency output device, said just-named circuit means including means to attenuate all frequencies supplied to said call device except said ringing frequency and to attenuate said ringing frequency from the frequencies supplied to said audio frequency output device.

Claim 6

A relaying system comprising a transmitting network having first and second input means and an output means, said transmitting network being effective to provide a frequency modulated output signal at its output means in response to an alterable signal supplied to said first input means and to amplitude modulate said output signal in response to a variable signal supplied to said second input means, said network including attenuating means attenuating the frequencies below a minimum predetermined frequency at which said signal is amplitude modulated, a receiving network having network having an input means adapted to receive said output signal and having first and second output means, said receiving network being effective to provide an output at its said first output means which is derived from the frequency modulated portions of said signal when supplied to its said input means and to provide an output at its said second output means which is derived from the amplitude modulated portions of the signal supplied to its said input means, the magnitude of the frequency change of said frequency modulated output signal being no greater than the maximum frequency which is attenuated by said attenuating means.

Claim 7

A relaying system comprising a transmitting network having first and second input means and an output means, said transmitting network being effective to provide a frequency modulated output signal at its output means in response to an alterable signal supplied to said first input means and to amplitude modulate said output signal in response to a variable signal supplied to said second input means, said network including attenuating means attenuating the frequencies below a minimum predetermined frequency at which said signal is amplitude modulated, a receiving network having network having an input means adapted to receive said output signal and having first and second output means, said receiving network being effective to provide an output at its said first output means which is derived from the frequency modulated portions of said signal when supplied to its said input means and to provide an output at its said second output means which is derived from the amplitude modulated portions of the signal supplied to its said input means, the magnitude of the frequency change of said frequency modulated output signal being no greater than the maximum frequency which is attenuated by said attenuating means.

Claim 8

The combination of claim 5 in which there is provided a ringing frequency source, means connecting said ringing source to said transmitting network, said ringing source being effective to amplitude modulate said output signal of said transmitting network at a frequency which is intermediate said maximum attenuated frequency and said magnitude of the frequency change of said frequency modulation.

Claim 9

The combination of claim 6 in which there is provided a call device connected to said receiving network and energized thereby in response to the reception by said receiving network of said output signal when amplitude modulated by said ringing source, a receiving device connected to said second output means of said receiving network for energization by said output of said output means, said receiving network further including means attenuating said frequencies of said output of said second output means which is supplied to said receiving device which are of the same magnitude as provided by said ringing frequency source.

Claim 10

The combination of claim 7 in which means is provided to attenuate all frequencies which are supplied to said device except those at the frequency of said ringing frequency source.

Claim 11

The combination of claim 6 in which there is provided a call device connected to said receiving network and energized thereby in response to the reception by said receiving network of said output signal when amplitude modulated by said ringing source, said receiving network further including means attenuating said frequencies which are supplied to said call device whicH are not of the same magnitude as provided by said ringing frequency source.

Claim 12

The combination of claim 5 in which said transmitting network is provided with power controlling means controlling the power of said output signal, said power controlling means being effective to maintain a first power magnitude of said output signal when said alterable signal supplied to said first input means has a first characteristic and to maintain a second power magnitude of said output signal when said alterable signal supplied to said first input means has a second characteristic, said power controlling means further being effective to limit the variations in the magnitude of said power of said output signal to magnitudes intermediate said first and second power magnitudes when said variable signal is supplied to said second input means.

Claim 15

The combination of claim 11 in which said attenuating means attenuates to a first minimum magnitude all of those frequencies at which said signal is amplitude modulated which are less than the difference in the change in frequency of said output signal caused by said alterable signal, a ringing oscillator connected to said transmitting network and effective to amplitude modulate said output signal at a desired frequency, said desired frequency being greater than said first minimum magnitude, said attenuating means being effective to attenuate the amplitude modulation of said output signal at said desired frequency.

Claim 16

The combination of claim 12 in which said attenuating means comprises a filter in which said first minimum magnitude of attenuation is in the range of 15 db. and in which the magnitude of attenuation of said desired frequency is in the range of not less than 3 db.

Claim 17

The combination of claim 13 in which said predetermined frequency change is in the range of 200 Hz and said desired frequency is in the range of a frequency of 350 Hz, said filter further attentuating all signals up to a frequency of 500 Hz not less than a range of 3 db.

Claim 18

The combination of claim 11 in which said transmitting network is provided with power controlling means controlling the power of said output signal, said power controlling means being effective to maintain a first power magnitude of said output signal when said alterable signal supplied to said first input has a first characteristic and to maintain a second power magnitude of said output signal when said alterable signal supplied to said first input means has a second characteristic, said power controlling means further being effective to limit the variation in the magnitude of said power of said output signal to magnitudes intermediate said first and second power magnitudes when said variable signal is supplied to said second input means.

Claim 21

The combination of claim 16 in which there is provided a call bell, a band-pass filter, means connecting said call bell to said second output means and including said band-pass filter, said attenuating means comprising a high-pass filter, said band-pass filter being tuned to a frequency greater than the difference in frequency between said first and second frequencies, said high-pass filter being tuned to attenuate frequencies at least as great as the frequency to which said band-pass filter is tuned.