and speech input to four remote locations. One shall be used for an all-call key. A 24 volt relay power supply rectifier, a preamplifier, and a terminal block shall be installed and wired within the turret. 17-24. The Relay Power Supply shall be RCA type MI-12501 or equal, and have the fol wing characteristics: Rated output, one ampere;Ripple, less than 0.5 volts at rated output; Maximum zero load voltage, 33 V.D.C.; full load voltage, 24 V.D.C.; Power supply 105 to 125 V.A.C.; 50/ 60 cycles; Power consumption, 1.3 amperes A.C. 17-25. The preamplifier or voltage amplifier shall be RCA type MI-12242 or equal. impedance input. It shall have a low It shall have flat characteristics from 30 to 10,000 C.P.S. Its rated output shall be plus 18 db with less than 1.5% distortion at 1000 C.P.S. It shall have an overall gain of 77 db. 17-26. A Cannon Type XL Plug or equal shall be supplied in the console to accommodate microphone input. 17-27. Each Microphone shall be RCA MI-12004 or equal. It shall be of the dynamic type with 250 ohm output. Output level shall be minus 57 db; 75 to 9,000 cycles. frequency response It shall be equipped with a desk stand and a 15 ft. cord terminated with a Cannon or equal plug. 17-28. Each of the Power Amplifiers shall be RCA type MI-12188 or equal in an RCA type MI-12666 x 1/2 or equal cabinet. It shall be of the bridging type, capable of 70 watts output with less than 5% distortion, 100 to 7,500 C.P.S. It shall have a frequency response flat from 30 to 15,000 C.P.S. within 1 db. It shall employ four 807 type tubes in a parallel push-pull power output circuit. It shall heve an overall gain of 41qdb. It shall have a 24 volt relay interrupting its plate circuit. It shall have a volume control. It shall he mounted and wired in a steel cabinet with a hinged locking door. A terminal block, terminating all input and output circuits of the net work shall be installed within the cabinet. 17-29. Hach of the loudspeakers shall consist of an RCA type MI-6303 speaker, type MI-6306 driver, type MI12371 transformer, and type MI-6399 cover or equal. Loudspeakers shall be 5-1/2' re-entrant trumpets flared from an exponential formula equipped with 60 watt 17-4