A variable speed drive having a rectifier, an inverter, an inverter modulator, an inverter controller, and a control loop, for controlling a motor load, wherein the control loop reduces an amount of power transferred to the inverter during a voltage sag. The transmitter circuit includes a transmission driver which drives a signal line for the DP and a transmission driver which drives a signal line for the DM. In certain embodiments, the compressor-expander comprises one or more stages, each stage consisting of pressure vessel partially filled with water or other liquid. The lip is desirably integrally formed in the table top as part of a unitary structure and the lip includes a generally hollow interior that is integrally formed during the blow-molding process with the generally hollow interior of the table top.