SPECIFICATIONS Type: Frequency Response: Output Impedance: Output Level: Pickup Pattern: Hum: Protection: Dimensions: Weight: Finish: Cardioid 40 to 10,000 cycles 30/50 ohms -- 56 dbm/10 dynes/cm2 639A -- 3-directional pattern 639B -- 6-directional pattern -- 120 db (Ref.: 10-3 Gauss) Two stage wind screen height -- 7'/e" (including plug) Width -- 3 7/16" Depth - - 4 7/16" 3 1/4 lbs. Instrument grey ACCESSORIES See "Microphone Accessories" sheet for suspension, floor or desk stand mountings, adapters, and other microphone accessories. ARCHITECTS AND ENGINEERS SPECIFICATlONS The microphone shall be of the directional type employing both a dynamic moving coil pressure element and a ribbon-type velocity element, assembled in a streamlined housing, arranged so that their outputs can either be used individually or combined equally. The directivity patterns so provided shall be selectable through a screwdriver operated switch mounted Rush on the microphone housing. The patterns provided by combining the outputs of these elements shall be cardioid in form. The average discrimination between the front and back of the microphone shall be not less than 20 db over the range of 40 to 10,000 cycles per second. In the range from 70 to 7,000 cycles, the minimum discrimination at any frequency shall be 15 db. The construction of the microphone shall incorporate a two stage wind screen for protection of the velocity element. The microphone shall have (select one) (A) 3 positions, (B) 6 positions. It shall have a smooth response and not deviate from the average more than +- 4 db over the range from 40 to 10,000 cycles. The average impedance throughout this range shall be on the order of 40 ohms. The output level shall be -- 56 dbm/10 dynes/cm2. The hum shall be no greater than -- 120 db (Ref.: 10 " Gauss). The microphone shall measure no greater than 7 1/2" high (including plug), 3~i~" wide, and 4 7/16" deep. It shall weigh on the order of 3 1/4 lbs. in order that a magnetic struc- ture of proper size is usable in the construction of the unit. The microphone shall be finished in instrument grey, and shall be so constructed as to be adaptable to mount- ing either by suspension or on stands. The microphone shall be Altec Lansing Model 639 (select one) (A) 3 pattern, or (B) 6 pattern.