The Type 1205-B Adjustable Regulated Power Supply (Figure 1) is a compact, high-efficiency, fast-response source of regulated power from 0 to 300 volts, up to 200 ma. The Type 1205-B also includes two 5-amp 6.3-volt supplies and a regulated -150-volt 5-ma bias supply. 1.2 DESCRIPTION. 1.2.1 CONTROLS. Three controls are mounted on the front panel: A POWER toggle switch with a standby (B + OFF) position, a METER toggle switch to select either a voltage or a current meter indication, and an OUTPUT VOLTAGE control, by which the output voltage may be varied from 0 to full voltage. 1.2.2 CONNECTORS. The front-panel output connectors are all jack-top binding posts. The three on the right-hand end are, from top to bottom, the B+, B- (or bias +), and bias (-) connectors. A binding post adjacent to the B + and B- posts permits grounding either B+ or B-. Two pairs of binding posts, labeled 6.3 v, are the terminals for the two ac heater supplies. These terminals may be connected for either series or parallel operation (refer to paragraph 3.2). The line-voltage cable is attached to the power supply at the left side of the instrument. Unit Instruments being powered by the Type 1205-B may be plugged directly into the multipoint connector at the right-hand side of the power supply. Connections are shown in Figure 7. 2 PRINCIPLES OF OPERATION 2.1 GENERAL. (See Figure 2). The Type 1205-B consists basically of two parts: a series-tube regulator, and a thyratron control rectifier. The series regulator provides fast response, low-drift, and low output impedance over a wide frequency range. The usual high dissipation of such a circuit is averted by use of a thyratron control rectifier, which maintains a constant voltage drop across the series regulator.