An implantable microstimulator configured to be implanted beneath a patient’s skin for tissue stimulation employs a bi-directional RF telemetry link for allowing data-containing signals to be sent to and from the implantable microstimulator from at least two external devices. The housing has a first non-conductive layer and a second non-conductive layer. The monitoring system emits a monitoring beam to image the target region during a monitoring period. A difference can then be calculated between the student speech sample duration disparity and the reference speech sample duration disparity. Each transducer is energized to produce a sonic pulse which, dependent on the application, has a carrier frequency of at least 200 kHz. In addition, the gate terminal of the first transistor is connected via a first resistor to a first pole of a voltage source and the gate terminal of the second transistor is connected via a second resistor to a second pole of the voltage source.