US 4,400,584 A · Speakerphone for radio and, landline telephones

Abstract

An improved speakerphone (120 and 130 in FIG. 1) for radio and landline telephones is described. The improved speakerphone (120 and 130) includes a microphone (102 and 132), a speaker (104 and 134) and unique control circuitry (106 and 136). The control circuitry of speakerphone (200 in FIG. 2) interfaces a microphone (250) to a transmit signal (220) and speaker (260) to a receive signal (222) of a duplex communication path, such as a radio channel or telephone line. An audio switch (212) opens or closes the speaker audio path in response to a control signal (224) from control logic (230), and another audio switch (202) opens or closes the microphone audio path in response to the binary complement of the control signal (224). Transmit and receive signal detectors (206 and 207), each includes a logarithmic amplifier (240), an envelope detector (241), a smoothing filter (245 ), a valley detector (242), a summer (243) and a comparator (244) for detecting the presence of audio signals in environments that may be subject to high background noise. Binary output signals from the transmit and receive signal detectors (206 and 207) are applied to control logic (230) which generates the control signal (224) for opening and closing the transmit and receive audio paths. The control logic (230 in FIG. 3) includes delay circuitry (316 and 318) and logic circuitry (304, 306, 308, 310, 312 and 314) for setting and resetting a flip-flop (302) storing the control signal (224). The control logic (230) changes the state of the control signal flip-flop (302) for switching the audio path between the micorphone and speaker when audio signals from the presently closed audio path have not been detected for a time interval determined by the delay circuitry (316 and 318) and audio signals thereafter are detected on the other audio path.

Claims27

Dependent claims

Circuitry for controlling the application of audio signals from a communication path to utilization means and the application of audio signals from an audio signal source to the communication path, comprising:

first and second detecting means for detecting the presence of audio signals from the communication path and the audio signal source, respectively, and each generating an output signal having a first state when audio signals are present and a second state when audio signals are absent;
first generating means for generating an output signal having a first state when the second detecting means output signal has a first state, and a second state when both the second detecting means output signal has a second state and the first detecting means output signal changes from the second state to the first state;
second generating means for generating an output signal having a first state when the first detecting means output signal has a first state, and a second state when both the first detecting means output signal has a second state and the second detecting means output signal changes from the second state to the first state;
first and second delay means, coupled to the first and second detecting means, respectively, for each generating an output signal having a first state when the corresponding detecting means output signal has a first state, and having a second state a predetermined time interval after the corresponding detecting means output signal has a second state;
control means for generating a control signal having a first state in response to the second state of the second delay means output signal, the second state of the first generating means output signal and the first state of the first detecting means output signal, and a second state in response to the second state of the first delay means output signal, the second state of the second generating means output signal and the first state of the second detecting means output signal;
first switching means responsive to the first state of the control signal for applying audio signals from the communication path to the utilization means;
and
second switching means responsive to the second state of the control signal for applying audio signals from the audio signal source to the communication path.

5 more elements

Circuitry for controlling the application of audio signals from a communication path to speaker means and the application of audio signals from an microphone means to the communication path, comprising:

first and second detecting means for detecting the presence of audio signals from the communication path and the audio signal source, respectively, and each generating an output signal having a first state when audio signals are present and a second state when audio signals are absent;
first generating means for generating an output signal having a first state when the second detecting means output signal has a first state, and a second state when both the second detecting means output signal has a second state and the first detecting means output signal changes from the second state to the first state;
second generating means for generating an output signal having a first state when the first detecting means output signal has a first state, and a second state when both the first detecting means output signal has a second state and the second detecting means output signal changes from the second state of the first state;
first and second delay means, coupled to the first and second detecting means, respectively, for each generating an output signal having a first state when the corresponding detecting means output signal has a first state, and having a second state a predetermined time interval after the corresponding detecting means output signal has a second state;
control means for generating a control signal having a first state in response to the second state of the second delay means output signal, the second state of the first generating means output signal and the first state of the first detecting means output signal, and a second state in response to the second state of the first delay means output signal, the second state of the second generating means output signal and the first state of the second detecting means output signal;
first switching means responsive to the first state of the control signal for applying audio signals from the communication path to the speaker means;
and
second switching means responsive to the second state of the control signal for applying audio signals from the microphone means to the communication path.

5 more elements

A method for controlling the application of audio signals from a communication path to utilization means and the application of audio signals from an audio signal source to the communication path, said method comprising the steps of:

detecting the presence of audio signals from the communication path and generating a first output signal having a first state when audio signals are present and a second state when audio signals are absent;
detecting the presence of the audio signals from the audio signal source and generating a second output signal having a first state when audio signals are present and a second state when audio signals are absent;
generating a third output signal having a first state when the second output signal has a first state, and a second state when both the second output signal has a second state and the first output signal changes from the second state to the first state;
generating a fourth output signal having a first state when the first output signal has a first state, and a second state when both the first output signal has a second state and the second output signal changes from the second state to the first state;
generating a fifth output signal having a first state when the first output signal has a first state, and a second state a predetermined time interval after the first output signal has a second state;
generating a sixth output signal having a first state when the second output signal has a first state, and a second state a predetermined time interval after the second output signal has a second state;
control means for generating a control signal having a first state in response to the second state of the sixth output signal, the second state of the third output signal and the first state of the first of the first output signal, and a second state in response to the second state of the fifth output signal, the second state of the fourth output signal and the first state of the second output signal;
applying audio signals from the communication path to the utilization means in response to the first state of the control signal;
and
applying audio signals from the audio signal source to the communication path in response to the second state of the control signal.

7 more elements

Dependencies are inferred from the claim text.

Speakerphone for radio and, landline telephones

Life of this patent

Speakerphone for radio and, landline telephones

Life of this patent

Abstract

Claims27