The Type 1304-B Beat-Frequency Audio Generator (Figure 1) is a signal generator capable of supplying up to 1 watt into a 600-ohm load at frequencies between 20 and 40,000 cycles per second. The Audio Generator is useful in amplitude-vs-frequency tests on audio-frequency equipment, and, as a general-purpose audio generator, is valuable as a power source for bridge measurements, as a modulator for r-f signal generators, and as a test source for acoustic work at both audio and ultrasonic frequencies. The Audio Generator can be coupled to an automatic analyzer or recorder. 1.2 DESCRIPTION. 1.2.1 GENERAL. The Audio Generator is mounted in a heavy-gauge aluminum cabinet, which is equipped with aluminum end frames for table use. If desired, the end frames can be removed and the instrument mounted in a 19-inch relay rack. Supplied with the Type 1304-BR (Relay-Rack Model)Audio Generator are special rack-mounting brackets, which secure cabinet and instrument to the rack, permitting either to be withdrawn independently of the other. Instructions for installing the Type 1304-BR in a relay rack accompany these brackets.