Efficient apparatus, methods, systems and devices to generate, transmit and detect optical differential polarization-phase-shift keying signals are disclosed for high spectral efficiency optical communication systems. The apparatus comprising a phase locked loop cluster. After the caller enters the telephone number of the subscriber, the service places a query to an SCP. The system is arranged to move the first set of transducers, the second set of transducers and the third set of transducers in a tangential direction with respect to the transport direction along an interior wall of the pipeline. The ear bud device can be modified to receive analog or digital inputs from other outside sources. The slots are closed by the combustor dome to provide cooling holes when the heat shield is mounted on the combustor.