Model 305 Phasemeter (figure 1-1) represents a totally new concept in the measurement of phase angle. A precision phase angle measurement is obtained simply by connecting the signals and reading the display. No adjustments are required during normal use. Model 305 senses the signal frequency and adjusts its output time constant for maximum speed commensurate with low ripple. It remains operational in the presence of up to 10% high frequency noise. Model 305 sensitivity to waveform distortion is reduced over that of other phasemeters which normally require filters to remove distortion effects. 1-5. The use of the automatic dual mode switching allows for continuous phase plotting between <-160° to > +340° with no discontinuities. The front panel controls on Model 305 main frame are used only for self checking of the main frame and calibration of remotely connected accessories such as a recorder or printer. 1-6 . Standard plug-in units covering a frequency range of 1 Hz to 11 MHz are available with Model 305 Phasemeter. Special plug-in units are available on request. 1-7. SPECIAL FEATURES 1-8. Model 305 provides special features when used with Plug-in Model 305-PA-3001 or 305-PA-3002. a. No operating controls. b. Excellent stability -~ no operating adjustments. c. 0.05° accuracy independent of input voltage. d. Versatile plug-in concept. e. Basic frequency range: 2 Hz to 700 kHz (extendable to I Hz or 11 MHz with other plug-ins). f. Digital readouts on Models 305B, 305C and 305D. g. Digital outputs on Models 305B, 305C and 3&5D-for use with printers, etc. h. 1 Megohm input impedance. i. Levels extendable to 40 KV using Tektronix probes. j. Indicator lights on each input to indicate either low or high input levels (305-PA-3001 only). k. High overvoltage capability.