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 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.