Loudspeaking telephone with a frequency shifting circuit

Claim 2

A voice switched type loudspeaking telephone comprises: means for comparing the levels of a sending voice signal and a receiving voice signal to produce a level comparison between said levels; first frequency shifting means in a transmitting path responsive to said level comparison for frequency-shifting a signal in said transmitting path; second frequency shifting means in a receiving path responsive to said level comparison for frequency-shifting a signal in said receiving path; first level control means in said transmitting path responsive to said level comparison for level-controlling a signal in said transmitting path; and second level control means in said receiving path responsive to said level comparison for level-controlling a signal in said receiving path.

Claim 3

A voice switched type loudspeaking telephone comprising: means for comparing the levels of a sending voice signal and a receiving voice signal to produce a level comparison between said levels; transmitting path frequency shifting means in said transmitting path responsive to said level comparison for frequency-shifting a signal in only said transmitting path, if the level of said receiving voice signal is higher than the level of said sending voice signal; receiving path frequency shifting means in said receiving path responsive to said level comparison for frequency-shifting the signal in only said receiving path, if the level of said sending voice signal is higher than the level of said receiving voice signal; and transmitting path level controlling means in said transmitting path responsive to said level comparison for level-controlling a signal in only said transmitting path, if the level of said receiving voice signal is higher than the level of said sending voice signal; and receiving path level controlling means in said receiving path responsive to said level comparison for level-controlling the signal in only said receiving path, if the level of said sending voice signal is higher than the level of said receiving voice signal.

Claim 4

A voice switched type loudspeaking telephone comprising: means for comparing the levels of a sending voice signal and a receiving voice signal to produce a level comparison between said levels; transmitting path frequency shifting means in said transmitting path responsive to said level comparison for frequency-shifting a signal in only said transmitting path, if the level of said receiving voice signal is higher than the level of said sending voice signal; receiving path frequency shifting means in said receiving path responsive to said level comparison for frequency-shifting the signal in only said receiving path, if the level of said sending voice signal is higher than the level of said receiving voice signal; and transmitting path level controlling means in said transmitting path responsive to said level comparison for level-controlling a signal in only said transmitting path, if the level of said receiving voice signal is higher than the level of said sending voice signal; and receiving path level controlling means in said receiving path responsive to said level comparison for level-controlling the signal in only said receiving path, if the level of said sending voice signal is higher than the level of said receiving voice signal.

Claim 5

A loudspeaking telephone as claimed in claim 2, wherein each of said transmitting path and receiving path frequency shifting means comprises: an oscillator for producing a signal oscillating at a predetermined frequency; first filter means for limiting said transmitting and receiving path signals with respect to their frequency bandwidth; first frequency divider means for dividing said predetermined frequency from said oscillator by a predetermined number in order to produce an output; first balanced modulator means for balance-modulating an output of said first filter means by said output of said first frequency divider means; second filter means for limiting an output of said first balanced modulator means with respect to a frequency band in order to produce an output; variable frequency divider means for dividing said predetermined frequency from said oscillator based on said level comparison; second balanced modulator means for balance-modulating said output of said second filter means by an output of said variable frequency divider means; and third filter means for limiting an output of said second balanced modulator means with respect to a frequency bandwidth in order to output said voice signals.

Claim 6

A loudspeaking telephone as claimed in claim 2, wherein each of said transmitting path and said receiving path frequency shifting means comprises: an oscillator for producing a signal oscillating at a predetermined frequency; first filter means for limiting said transmitting and receiving path signals with respect to their frequency bandwidth; first frequency divider means for dividing said predetermined frequency from said oscillator by a predetermined number in order to produce an output; first balanced modulator means for balance-modulating an output of said first filter means by said output of said first frequency divider means; second filter means for limiting an output of said first balanced modulator means with respect to a frequency band in order to produce an output; voltage controlled oscillator means for producing a signal oscillating at a frequency which is associated with said level comparison; second balanced modulator means for balance-modulating said output of said second filter means by an output of said voltage controlled oscillator means; and third filter means for limiting an output of second balanced modulator means with respect to a frequency band in order to produce a frequency-shifted signal of said transmitting and receiving path signals.