Abstract: A portable communication system includes a remote speaker microphone (RSM) accessory (102) coupled to a portable radio and further coupled to a secondary audio accessory (SAA) (108). The RSM accessory (102) includes a user interface toggle switch (120) that toggles between a first mode of operation and a second mode of operation. Toggling to the first mode of operation selectively routes receive audio from the portable radio to a speaker (112) of the RSM accessory, while generating and routing a periodic audio artifact from the RSM to the SAA (108) for play out at a speaker (316) of the secondary accessory. The received audio is played out of the RSM speaker (112) in parallel with the periodic audio artifact being played out of the secondary accessory speaker (316).

Abstract: An audio accessory with high and low impedance paths to a speaker is provided, and a radio therefor. The audio accessory comprises: a speaker; an audio interface to connect to a respective audio interface of the radio; a switching circuit comprising: high and low impedance paths; and a switch to connect the audio interface to the speaker via one of the high and low impedance paths, the switch initially connecting the audio interface to the speaker via the high impedance path. The accessory further comprises a data interface to connect to a respective data interface of the radio; and a controller to: in response to receiving, via the first data interface, from the radio, a message to control the switch to connect the audio interface to the speaker via the low impedance path, control the switch to connect the audio interface to the speaker via the low impedance path.

Abstract: An audio accessory with high and low impedance paths to a speaker is provided, and a radio therefor. The audio accessory comprises: a speaker; an audio interface to connect to a respective audio interface of the radio; a switching circuit comprising: high and low impedance paths; and a switch to connect the audio interface to the speaker via one of the high and low impedance paths, the switch initially connecting the audio interface to the speaker via the high impedance path. The accessory further comprises a data interface to connect to a respective data interface of the radio; and a controller to: in response to receiving, via the first data interface, from the radio, a message to control the switch to connect the audio interface to the speaker via the low impedance path, control the switch to connect the audio interface to the speaker via the low impedance path.

Abstract: An apparatus and method for controlling an audio power circuit. The audio power circuit includes an audio amplifier having a power input and a speaker connected to the audio amplifier. The audio power circuit also includes a control circuit configured to be connected to a battery and the power input and to control a supply of power to the power input. The audio power circuit further includes a thermal protection circuit connected between the audio amplifier and the speaker, the thermal protection circuit configured to generate a thermal protection signal and provide the same to the control circuit, wherein the control circuit is further configured to control the supply of power based on the thermal protection signal.

Abstract: An apparatus and method for controlling an audio power circuit. The audio power circuit includes an audio amplifier having a power input and a speaker connected to the audio amplifier. The audio power circuit also includes a control circuit configured to be connected to a battery and the power input and to control a supply of power to the power input. The audio power circuit further includes a thermal protection circuit connected between the audio amplifier and the speaker, the thermal protection circuit configured to generate a thermal protection signal and provide the same to the control circuit, wherein the control circuit is further configured to control the supply of power based on the thermal protection signal.

Abstract: An intrinsically safe audio power circuit includes redundant electronic fuses disposed between the power input of an audio power amplifier and the battery source of the portable two-way radio device. The electronic fuse circuits are connected in series with each other, and each electronic fuse circuit includes a series switch transistor that can shut off the flow of current between the battery and the audio power amplifier. Each electronic fuse circuit also includes a current sense portion, and when the current through the electronic fuse circuits reaches a current threshold, it will shut off its series switch transistor using an active bias circuit in order to ensure sufficiently rapid shut off.

Abstract: An intrinsically safe audio power circuit includes redundant electronic fuses disposed between the power input of an audio power amplifier and the battery source of the portable two-way radio device. The electronic fuse circuits are connected in series with each other, and each electronic fuse circuit includes a series switch transistor that can shut off the flow of current between the battery and the audio power amplifier. Each electronic fuse circuit also includes a current sense portion, and when the current through the electronic fuse circuits reaches a current threshold, it will shut off its series switch transistor using an active bias circuit in order to ensure sufficiently rapid shut off.