Method and apparatus for detecting switch closures

A remote control and earphones set for connection to an audio recording and playback device, the device having a four-pole socket which is electrically coupled to an audio circuit in the device for delivering a left and a right channel audio-frequency signal, a ground connection and a circuit for receiving an external control signal from a control line, the control line being pulled high by a pull-up resistor in the device, the remote control and earphones set comprising:

• a four-pole jack for connecting to the four-pole socket of the device;
• a remote control coupled to the four-pole jack, the remote control having:
• a resistance formed by a network of resistors, wherein the resistors are connected in series;
• a plurality of switches electrically coupled to the network of resistors from the resistance, the closure of each switch denoting the activation of one of a set of audio operations, the set of audio operations comprising recording and playback, wherein each of the plurality of switches is associated with a corresponding number of resistors in the series or resistors and wherein the switch denoting the activation of a recording audio operation is associated with the least number of resistors;
• and
• a microphone electrically coupled at one end to the control line and at the other end to the resistance for converting received sound to an audio-frequency signal onto the control line during recording, the resistance and the microphone cooperating with the pull-up resistor to form a voltage divider;
• a pair of earphones electrically coupled to the four-pole jack for receiving the audio-frequency signals during playback;
• and
• whereby the closure of each switch leaves a different number of resistors in the resistance in the voltage divider to produce a predetermined voltage on the control line for the device to identify which switch is closed.

A method of detecting the closure of one of a plurality of switches which is coupled to a single input line of a microprocessor in a device powered by a battery source, the device being operable over a range of battery levels of the battery source, the method comprising:

• generating a predetermined voltage, which is dependent on the battery level, at the input line when a switch in the plurality of switches is closed;
• converting the predetermined voltage received on the input line to a digital voltage value;
• measuring the battery level by converting an analog battery level to a digital value;
• selecting a set of predetermined voltage values corresponding to the digital value of the battery level;
• and
• comparing the digital voltage value with the selected set of predetermined voltage values to determine which of the plurality of switches is closed.

Apparatus for detecting the closure of one of a plurality of switches using a single input line of a detector, the apparatus comprising:

• a voltage generator configured to be responsive to a switch closure for generating an output voltage on the input line, the output voltage being one of a plurality of predetermined voltages depending on which one of the plurality of switches is closed, wherein the voltage generator comprises a voltage divider having:
• a first resistance;
• and
• a second resistance electrically coupled to the first resistance at a control node,
• the second resistance comprising a network of resistors connected in series and electrically coupled to the plurality of switches;
• a microphone, electrically coupled in series with the second resistance of the voltage generator, for converting sound received thereat to audio-frequency signals on the input line;
• a pair of earphones electrically coupled to the input line for receiving the audio-frequency signals during playback;
• a comparator in the detector for receiving the output voltage on the input line and for determining which one of the plurality of switches is closed;
• and
• a storage means that is activated for storing audio-frequency signals on the input line when one of the switches designated as a recording function switch is detected to be closed.

A remote control and earphones set for connection to an audio recording and playback device, the device having a four-pole socket which is electrically coupled to an audio circuit in the device for delivering a left and a right channel audio-frequency signal, a ground connection and a circuit for receiving a external control signal from a control line, the control line being pulled high by a pull-up resistor in the device, the remote control and earphones set comprising:

• a four-pole jack for connecting to the four-pole socket of the device;
• a remote control coupled to the four-pole jack, the remote control having:
• a resistance formed by a network of resistors wherein the resistance cooperates with the pull-up resistor to form a voltage divider, wherein the resistors in the network of resistors are connected in series;
• a plurality of switches electrically coupled to the network of resistors from the resistance, the closure of each switch denoting the activation of one of a set of audio operations, the set of audio operations comprising recording and playback, wherein each of the plurality of switches is associated with a corresponding number of resistors in the series of resistors and wherein the switch, denoting the activation of a recording audio operation is associated with the least number of resistance;
• a microphone, switchably connectable across at least one resistor of the resistance via a microphone on/off switch, for converting received sound to an audio-frequency signal onto the control line during recording;
• and
• a pair of earphones electrically coupled to the four-pole jack for receiving the audio-frequency signals during playback;
• and whereby the closure of each switch leaves a different number of resistors in the resistance in the voltage divider to produce a predetermined voltage on the control line for the device to identify which switch is closed, and wherein the microphone on/off switch and one of the switches designated a recording function switch is a common double-pole-single-throw switch configured such that the microphone is switched across the at least one resistor when the recording function switch is closed.

A method of detecting the closure of one of a plurality of switches which is coupled to a single input of a microprocessor in a device powered by a battery source, the device being operable over a range of battery levels of the battery source, the method comprising:

• generating a predetermined voltage, that is dependent on the battery level, at the input line when a switch in the plurality of switches is closed, wherein each of the plurality of switches is associated with a corresponding number of resistors in a series of resistors;
• activating a microphone electrically coupled in series with the resistors when the switch associated with the smallest number of resistors is closed;
• converting the predetermined voltage received on the input line is a digital voltage value;
• measuring the battery level by converting an analog battery level to a digital value based on a fixed reference voltage obtained from the battery;
• selecting a set of predetermined voltage values corresponding to the digital value of the battery level;
• and
• comparing the digital voltage value with the selected set of predetermined voltage values to determine which of the plurality of switches is closed.

A method of detecting the closure of one of a plurality of switches which is coupled to a single input line of a microprocessor in a device powered by a battery source, the device being operable over a range of battery levels of the battery source, the method comprising:

• coupling a microphone to the input line;
• generating a predetermined voltage at the input and interrupting a microprocessor when a switch in the plurality of switches is closed;
• and
• under the instruction of the microprocessor,
• converting the predetermined voltage received on the input line to a digital voltage value;
• measuring the battery level;
• selecting a set of predetermined voltages corresponding to the battery level;
• comparing the digital voltage value with the selected set of predetermined voltages to determine which of the plurality of switches is closed;
• and
• changing the voltage on the input line to appropriately bias the microphone such that an audio-frequency signal received from the microphone is at least substantially undistorted when it is determined that one of plurality of switches designated as a recording function switch is closed.