Communications headset power provision
View Patent ↗Electric power is provided to a two-way communications headset by creating a differential DC voltage potential between a ground conductor associated with a microphone of that headset and a ground conductor associated with an acoustic driver of that headset, thereby enabling that headset to refrain from drawing electric power from a more limited local power source.
1. A power injection circuit to provide electric power to an aviation headset, the power injection circuit comprising:
an aircraft intercom system (ICS) interface for connection to an ICS, the ICS interface including at least a voltage (VCC) connection, a microphone high (mic-high) connection, a microphone low (mic-low) connection, and a system ground (system-gnd) connection;
a headset interface comprising at least one connector to receive at least one connector of the headset;
an alternate microphone low (alt-mic-low) conductor coupled to the headset interface to conduct a signal of a microphone of the headset;
a system ground conductor coupled to the ICS interface and the headset interface to couple a headset ground to the system ground connection;
a first voltage source coupled to the alt-mic-low conductor to create a DC voltage differential between the alt-mic-low conductor and the system ground conductor;
an alternate push-to-talk (alt-PTT) conductor coupled to the headset interface; and
a PTT separator coupled to the alt-PTT conductor to monitor the PTT conductor, and to signal the first voltage source to enable the first voltage source in response to detecting a triggering resistance between the alt-PTT conductor and the alt-mic-low conductor.
2. The power injection circuit of claim 1 , wherein:
the headset interface comprises a first connector and a second connector to receive two connectors of the headset;
the alt-mic-low conductor is coupled to the first connector; and
the system ground conductor is coupled to the second connector.
3. The power injection circuit of claim 1 , further comprising:
an alternate microphone high (alt-mic-high) conductor coupled to the interface to cooperate with the alt-mic-low conductor to conduct the signal of the headset;
a second voltage source; and
a resistor coupling the second voltage source to the alt-mic-high conductor to provide an alternate microphone bias voltage between the alt-mic-high conductor and the system ground conductor, wherein the alternate microphone bias voltage differs from an expected microphone bias voltage by a voltage similar to the DC voltage differential between the mic-low connection and the system ground connection.
4. The power injection circuit of claim 1 wherein:
the ICS interface further includes a PTT connection, and
the PTT separator couples the PTT connection to the mic-low connection with low resistance when it detects a low resistance between the alt-PTT connection and the alt-mic-low conductor.
5. The power injection circuit of claim 1 further comprising:
a DC-blocking capacitor coupling the mic-low connection to the alt-mic-low conductor in parallel with the injection voltage source, to pass voice-band signals from the alt-mic-low conductor to the mic-low connection, while blocking the DC voltage from reaching the mic-low connection.
6. The power injection circuit of claim 1 further comprising:
an alternate microphone high (alt-mic-low) conductor coupled to the headset interface to conduct the signal of a microphone of the headset; and
an alternate bias voltage source powered by the VCC connection and providing a first DC voltage on the alt-mic-high conductor relative to the mic-low connection.
7. The power injection circuit of claim 6 further comprising:
a DC-blocking capacitor coupling the mic-high connection to the alt-mic-high conductor, to pass voice-band signals from the alt-mic-high conductor to the mic-high connection, while blocking the first DC voltage from reaching the mic-high connection.
8. A system for powering active electronics within an aviation headset, the system comprising:
a power injection circuit comprising:
an aircraft intercom system (ICS) interface for connection to an ICS, the ICS interface including at least a voltage (VCC) connection, a microphone-high (mic-high) connection, a microphone-low (mic-low) connection, and a system ground (system-gnd) connection;
a first headset connection interface including at least one connector to receive at least one connector of the headset;
an alternate mic-low (alt-mic-low) conductor and an alternate push-to-talk (alt-PTT) conductor, each coupled to the first headset interface;
a system ground conductor coupled to the ICS interface and the first headset interface to couple a headset ground to the system ground connection;
an injection voltage source powered by the VCC connection and providing a DC voltage on the alt-mic-low conductor relative to the system ground conductor; and
a PTT separator coupled to the alt-PTT conductor to monitor the alt-PTT conductor, and to signal the injection voltage source to enable the injection voltage source in response to detecting a triggering resistance between the alt-PTT conductor and the alt-mic-low conductor; and
a headset power supply comprising:
a second headset connection interface for mating with the first headset connection interface and including at least a headset alt-mic-low connection, a headset alt-PTT connection, and a headset ground connection coupled to the headset ground;
an injected voltage tap circuit extracting the DC voltage between the headset alt-mic-low connection and the headset ground connection and providing the DC voltage to the active electronics within the headset as a power supply voltage; and
a triggering resistor connecting the headset alt-PTT connection to the headset alt-mic-low connection.
9. The system of claim 8 wherein the power injection circuit further comprises:
a DC-blocking capacitor coupling the mic-low connection to the alt-mic-low conductor in parallel with the injection voltage source, to pass voice-band signals from the alt-mic-low conductor to the mic-low connection, while blocking the DC voltage from reaching the mic-low connection.
10. The system of claim 8 wherein the power injection circuit further comprises:
an alternate microphone high (alt-mic-low) conductor coupled to the headset interface to conduct the signal of a microphone of the headset; and
an alternate bias voltage source powered by the VCC connection and providing a second DC voltage on the alt-mic-high conductor relative to the mic-low connection.
11. The system of claim 10 wherein the power injection circuit further comprises:
a DC-blocking capacitor coupling the mic-high connection to the alt-mic-high conductor, to pass voice-band signals from the alt-mic-high conductor to the mic-high connection, while blocking the second DC voltage from reaching the mic-high connection.
12. The system of claim 10 wherein:
the second headset connection interface includes a headset alt-mic-high connection; and
a third DC voltage existing between the headset alt-mic-high connection and the headset alt-mic-low connection is available to the microphone of the headset as a microphone bias voltage, the third DC voltage comprising the difference between the second DC voltage and the DC voltage from the injection voltage source.
13. An aviation headset for use with a power injection circuit, the headset comprising:
a headset interface by which the headset may be coupled to a matching headset interface of the power injection circuit, the headset interface including at least a microphone-high (mic-high) connection, a microphone-low (mic-low) connection, a push-to-talk (PTT) connection, and a ground connection;
an acoustic driver to acoustically output audio to an ear of a user;
an acoustic driver ground conductor coupling the acoustic driver to the ground connection of the headset interface;
a microphone to detect speech sounds of the user;
a microphone low signal conductor and a microphone high signal conductor coupling the microphone to the mic-low and mic-high connections, respectively, of the headset interface; and
an injected voltage tap circuit coupled to the ground connection and to the mic-low connection to receive electric power from a DC voltage differential between the ground connection and the mic-low connection provided by the power injection circuit; and
a triggering resistor connecting the PTT connection to the mic-low connection of the headset interface.
14. The headset of claim 13 , wherein the headset enters a failsafe mode in which the microphone and the acoustic driver continue to be useable with an ICS coupled to the headset interface in response to there being no DC voltage differential between the mic-low connection and the ground connection.