Fig. 6

If needed, one can use P-Channel JFET transistors (e.g., 2SJ177) operating as switches to divide the obtained acoustic signal into separate inspiratory and expiratory channels. In this arrangement, each of two P-Channel JFET transistors is configured such that the acoustic signal passing through from source (S) to drain (D) is blocked when the gate (G) is presented with a positive control voltage from the microcontroller. In the inspiratory channel, the microcontroller outputs a 5-V (blocking) control signal during the time that the LED is off (i.e., during expiration), while in case of the expiratory channel, the microcontroller outputs a 5-V (blocking) control signal during the time that the LED is turned on (i.e., during inspiration). Note that, the above circuit must be duplicated, once for the inspiratory channel and once again for the expiratory channel