The Type 1264-A Modulating Power Supply (Figure 1) is designed as a companion instrument to the Type 1361-A Oscillator and similar equipment to permit cw or square-wave-modulated operation of this instrument or pulse-modulated operation using an external pulse source. The Type 1264-A can be bolted directly to the Type 1361-A Oscillator to form a single assembly with all interconnections recessed between the adjacent end frames (see Figure 2). The composite instrument can readily be mounted in a relay rack by means of accessory panel extensions. With suitable accessory cables, the Type 1264-A can be used with the Type 1209-C, 1209-CL, 1215, or 1218 Unit Oscillator.