A circuit for dynamically combiningsplitting power amplifier outputs having at least four power input ports. The correspondence between this controlled voltage and the output load voltage determines the correspondence between the output current and the input current. At least one flow passage extends between one of the cooling channel and the shank cavity, toward the bucket cavity forward region. The baby monitor system further includes a plurality of transmitter faceplates that can be interchangeably connected to the faceplate connector of the transmitter housing.