In some embodiments, this invention pertains to isotopically enriched N-substituted piperazines. The boss has a polygonal drive head engageable with the drive opening of the attachment. The comparator compares the hold voltage signal with the reference voltage signal in response to a clock signal to generate a comparison output voltage signal. The front side is configured to support the electrical box and for snug installation of the cover plate. Alternatively, only one unit may be soldered on the semiconductor chip, and portions of the unit may be removed to fabricate the device. A single optical phase demodulator is used to demodulate the composite phase modulated optical beam to generate the combined RF signal.