Volume 4 1989 EARLY MICROPHONE HISTORY Bob Paquette ~1.ilwaukee, WI T llE TELEPHONE ERA The word 'microphone' comes from the Greek words •micro," meaning 'small,' and "phone• meaning 'sound." It fi~t appeared in a dictionary in 1683 as 'an instrument by whk:h small 10unds are intensi fied.' This wu in reference to acoustical bearing devices such as the ear trumpets ind megaphones of that era. Microphontli u v.e It.now them started with the fant articulate tele phone transmitter, ck."Veloped almOSl simultaneowly by Efuha Gray and Alexander Graham Bell Th.is was the liquid tranmiittcr of 1876 (Fig. 1). This transmitter would be classified as 1 variable-resistance device. Its operation was as folJCJW$: the user wlkcd into the black funnel-shaped mouthpiece, at the base of which is o Slrctched mem· brane diaphragm. A metlll pin through the center of the diaphragm ex· tends down into the metal cup below. The cup contains a dilute acid. An ohmmeter between the cup and the pin will show a fixed resistance. Any movement of the diaphragm will move the pin up und down in the liquid and the resistance will vary accordingly. If wires from the pin and cup were connected in series with a battery and telephone receiver, any talk directed into the mouthpiece would produce articulate speech in the receiver Mr. BeU did not want to use battery pov.cr with his telephone sy:>tem, so he tried to get around this obstade. ffis fint ICDCC! telephone sys tem in 1877 used two of his box telephones (Fig. 2) ,.,ith only we: no battery. ThCM: sets, referred to as magneto transmitten, .,ere actually telephone rcceivcn. A3 receivers they worked v.ell. but as transmitters their signal output was too weak to carry any great disuncc. Two of these box telephones, with three miles of wire betv.een them, required the user 10 shout in order to be heard. What was heard on the recciv· iog unit wus very foeble. So one can imagine how inconvenient this sys· tern was to u~e: first lo shout into the mouthpiece, then to listen in· tently at the mouthpiece for the called party's weak reply. Bell and his associates cnme to the conclusion that the transmiuer would have to be improved, which would then upgrade the whole &')'stem. 131 Fig. I. Bcll"s Liquid Transminer. Fig. 2. Bell's Finl Magiieto Telephone Fig. 3. !Zdison's t.umpblack Transmiucr. Fig. 4. Olnkc's Carbon· Block Transmitter with Desk StAnd. 132 2 4 Western Union entered the telephone bUlinC$$ late in 1877. Now, with two companies uyin& to develop a better transmitter, other ex perimenters be"'n to appear and offer their devices. Emile Berliner with his l~-oontact metal-to-metal transmitter, Edison with his many torms of carbon transmincrs and an clcc:uosiatic (condenser) design, Hughes' carbon rods. Blake's carbon block. and HuMinp' carboo granule type were a few of the new names and devices to appear. Both Berlinu and Hughes used the term •microphone' to desaibe their transmiuers. This was due to the high sensitivity or both of their de vices compared to the others. However, added sensitivity in these units resulted in more erratic behavior and reduced dependJbility. After the magneto type, the next improved tran~mitter to be put into use was Edison's lampblack carbon unit (f'ig. 3). another variable-resis tance de.rhone.' could handle up 10 15 amperes or current without burning up. One was a rondenser !}JM: (Fig. 9); the other was a water cooled carbon· granule !}pc he called his •11ough 1ran~itter" (Fig. 10). Europeun wircle!.S experimenters came up with a varied lot of high· power microphones between 1900 and 1915. J. Berliner (Telephone Mfg. Co. of Vienna) mude a high-current carbon microphone that was air cooled by 11 fnn mounted under the microphone, and an adjustable stand to go with it (Fig. 11). Anyone familiar with the inherent noise of an early carbon microphone can imagine what the signal-to-noise ratio was with this microphone, plus the added sounds of the motor and the rushing air BlondcU anJ Chambers had developed flame microphones in 1902 and 1910. BlondcU'' •name controUer" (Fig. 12) "'·orkcd as foUaws: A and A arc spad. rods in an oscillating circuit adjusted just short of sparking. Flame r is adjusted to reach up to the pp By speaking into mouthpiece: M, diaphragm D vibrates and alters the pressure of the ps supply, causina the Dame to change its length. As the name varies its entrance into the g,1p, the resistance between the g;ip points varies, and sparkin11 occurs in rci.ponse to its movements. Majoranna, Chambers, Vanni and Sykes had developed "liquid' or "hydraulic" microphones in 1906, 1910, 1912 and 1914 respectively. Majoranna's microphone (Fig. 13) worked as follows. A is the reser- 135 14 15 Fig. 14. Fcssendcn's *Microphone Rel:iy.• Fig. IS. C. Egner :ind J. G. l lolmstrom·s llil!h·Current Microphone. J6 I •I Fig. 16. Alexnnderson's Magnetic Modulator. Fig. 17 G. 8. Mnrzi's Carbon-Powder Microphone. voir that holds the conducting liquid that Dows down and out of B in a very fine stream C is an elastic diaphragm driven by a metal di aphragm E behind mouthpiece F About me feet from the reservoir the stream breaks inro droplets. A ser of contacts It is located at this point. Sound \'3riations on the diaphragm vary the pressure of the stream. Consequently, the thickness of the s1ream ar the contacts varies, producing a variable re:.istance in proportion 10 the sound on the diaphragm. Using a voltage of 6S vohs 11 12 amperes gives us 780 warts: a one-horsepower microphone! II is appropriate to point out one serious problem with this design. If someone would open or close the door 10 the room where the microphone was being used, it would create an air disturbance thar would move the stream out of the gap momentarily, rhus interrupting transmission. 136 Fessenden and Dubilier developed heavy-current microphone relays in 1906 and 1911 rcspectivc:Jy. A differential ma8f1etic relay was oper· ated by a telephone. It. in tum, operated a heavy-duly c:arbon transmit· ter in the antenna ciR:uit. These devices were c:apable of handling up to lS amperes of antenna currenL Figure 14 shows the Fessenden re. lay. Tucker and Koepsel experimented with "hot wire• microphones around 1907 but developed only specialized "large aun• detectors. One or the belier higll-current miaophones was developed by C Eg ner and J. G. Holmstrom of Stockholm in 1906. This microphone (Fig. 15) wu water-«>aled and consisted of 16 separate camon units. By connecting the carbon units in different series nnd parallel combina tions, various voltage.' and currents could be handled, from 10 volts at 20 amperes to 30 volts a1 10 amperes. 1n 1911 Alexanderson designed a special tran,former he called a •magnetic modulator" (Fig. 16) for use with his RF allemator. This unit could handle up to 75 lcilowatts. General Elect.ric made three smaller ~ersions or this unit with model numbers UT·l643 (.S to l.S amperes), lIT-1357 (1.S to 3.S A) and lTf-1367 (3.S to SA) These wue for the radio amateur using five- to 100-wall transnuuers. One other high-current microphone v.'orlh mentioning is one devel oped by G B. Mani of Comigliano, llaly (Fig. 17). The patent derines it as a •microphone with carbon powder fall for strong currents.• As the patent dCSCT!ption implies, it is another variable-resistance device using very fine carbon grains. The cup-shaped reservoir at the top holds the carbon grains that now througll a sci of con1act11, one of which is controlled hy the diaphragm. A cup In the base of the unit catche.' the used grains. When this cup is full, the user must stop talk· ing. remove the cup, transrer the contents to the upper reservoir, re· place the cup, and then continue the message. WORLD WAR I ~fiCR.OPHONES Lee de Forest in\ented the Audioo in 1906. rea:ived his patent in 1907, and introduced it to AT&T engineers in 1912. The Bell System. looking to replace its mechanical repea.ten with new technology, im· proved the vacuum tube and developed cirwitry not onlr for repeaters but also amplifiers and radio. World War I created immediate de mands for improved communications. Vacuum tubes not only helped meet these dcmnndll, but also put the microphone back into a simple circuit thut no longer required bulky, complex, high-current designs. Standard telephone transmitters could be used 11g11in, regMdless of the radio transmitter power. World Wnr I microphones were telephone transmitters adnptcd for use with the new tube-type equipment. JJ7 • 18 • Fig. 18. WE D-14298 (T-1). Fig. 19. Magnavox Noise-Canceling Microphone. 20 Fig. 20. WE T-12. Fig. 21. Western Electric 318W with Push-to-Talk Switch. 22 Fig. 22. Magnavox ST -4. Fig. 23. WE 360BW Microphone with 4A Horn. 138 19 21 23 Western Electric developed specific microphones such as the D- 14298 or T-1 (Fig. 18), to be used with their SCR-68 Army aircraft ra dio transmiuer. They also supplied n slight variation of this micro phone, the T-3, to General Electric. Ge in turn used it with the CG- 1104A radio transmilter i.et sold to the Navy. This was an early form of noise-camielling or "close-truking• microphone. Western Electric used their No. 326 dose-talking telephone transmiuer in the CW-930 hand microphone and the CW-1053 bulkhead microphone. These were used with the CW-936 S-wau radio trammiuer which they suppJ;ed to the Navy to use aboard submarine ch:isera. The Magnavox Company produced a noise-cancelling microphone (Fig. 19) for the Na~y to be used aboard its "mammoth NC planes.• This same microphone v.-as surplied to General Electric with a spray· shield cover. General Electric in turn supplied this microphone along v.ith othu equipment to the Navy. W~tem Electric provided the Anny with other microphones for apccial purposes. A No. 337 tde pbone transmitter was mounted on a wooden handle for some field eqwpmeot. WE also produced a 273W hand microphone and a T-12 band microphone (Fig. 20) using a 323BW transmiuer, to J;st a few. PUBLIC·ADlllU:SS l\Pl'l.ICATIONS Around 1915, Wei.tern Ehx:tric ~upplicd a very simple "loudspeaking oulfit" under two numcs, "Shawphonc• and "Chau-Phone.• The Shaw. phone was used for very srnnll pt1ging applicutions, while the Chau phone was for chauffeur-driven curs. Doth u-.:d the 318W hand micro phone with a 182 ho1 n and o bix-voh hnttery. The microphones (Fig, 21) were available in dull bl11ck, nickel und polished brass. After World War I. the radio indu.iry grew hy leaps and bounds. Radio amateurs were introducin11 the public to radio. Companies like Magnavox and Western Electric were introducing the populace to •public-address sy~tems." or 50und·reinforcement systems as we know them today. Magnavox. a smaU company on the West Co."\St, had developed a good born-type speaker and some small amplifiers Their experienre during the wu with special mi..,.ophoncs g;ive them the ~rtisc to manufacture a telephone for nou) arca.s. They also produced a sound ~em caUed ~elemepphone: This was :1 complete system oonsisling of a lacge 18-inch born Cnd microphones, while the plant stanch were used with the candlestick and other de.;k-type bousingi; like the Western Electric IA. Also, some crude wood stands were made with counter-balanced boom arms. Some of them had a rod extending out at waist height to keep the performer a proper distance from the microphone (Fig. 27). Some performers experienced "mike fright.' They would have a ten- 141 dency to freeze up when they approached the microphone, so attempts were made to disguise or hide it. This resulted in various types of mi crophone housings. RCA made a cloth.covered globe that was placed on a plant stand, with the microphone hidden inside. GE used a floor lamp and hid the microphone under the shade. The performer was told to sing by the lamp. Another problem with early singers, especially sopranos, was volume control. [f the performer did not keep a good distance (about two feet) from the microphone, 'blasting' would occur. This was, in reality, overloading the input circuitry and causing distor tion. Some engineers worried about sopranos singing high notes that might shatter their tubes! Some singers were asked to sing an octave lower, which brought about the new form of singing called •crooning" which became very popular. MICROPHONE MANUFACTURERS In the early Twenties, three major companies were producing micro phones: Westinghouse, Western Electric and General Electric. West inghouse put radio station KDKA on the air in 1920; KYW, WBZ and WJZ in 1921. Because proper microphones were not available, West inghouse began to custom-build them for ~his group of stations, conti.n uing up to about 1927. After the candlestick-telephone period they be gan to work on higher quality units. They modified and used a "phonetron' cone-type speaker (Fig. 28) which was later dubberl the 'dishpan• microphone. This was qujte an improvement over the tele phone transmitters since they aU had a squeaky high-pitched sound, whereas the 'phonetron• had bass and midran.ge which made it sound mellow in comparison. Their next generation of m icropb.ones were double-button carbons. The clamping rings were made of half-inch thick bakelite, the diaphragm was heavy paper with a strip of gold leaf on each side, and the bridges were light-weight brass with brass cups and felt washers. These microphones were put in felt-lined brass cylin ders about three and one-half inches long and about four inches in di ameter. The back was closed with a one-half inch thick piece of bake lite. The front was a brass end cap with a two and one-half inch open ing covered with fine brass screen. Three binding posts were provided under the mjcrophone for connections. All these units had tabs with holes for suspending them. Some units had wood bases with felt bot toms and the binding posts on the front of the wood base. Later a sim ilar cylinder with a condenser element patterned after the Western Electric condenser was provided. Because of their appearance (Fig. 29), they picked up the nickname "tomato can." In 1925 Westinghouse made a condenser microphone (Fig. 30) that was relatively portable. The old condenser element in the cylinder housing had to be within ten feet of a lowboy phonograph. console that contained the preamplifiers and power supply. The new condenser was 142 29 Fig. 28. Biroo1ge Stund with Modified Phoneiron Speaker. Nole "Distance' Rod on Stand Fig. 29. We~tinghouse 'Tomato Can' Microphone with Wood Base. 30 Fig. 30. WQtinghouse 1925 Condenser Microphone. Fig. 31. Westingho~e llus.haphooe. 31 built in10 a box that mea.uced 10-1/2 inche.. high by S-1 /2 inches wide by <4 inches deq> and had three compartmenis. The upper one con ~ the outpul tralbiormer; the ce.oier companmcnt held the con denser element; and 1he bottom space wu felt-lined and held the tube wrapped in fdl The tube was a ooo-microphonic P J2 type with leads - no socket An unusunl microphone produced by Westinghouse was 1he 'Hushaphone' (Fig. 31). This was a microphone for noisy areas. The radio studio bccnme busy ut times with one or two people preparing for a program and the unnouncer trying. for example, to give the news. The announcer could talk into this microphone and ii would not pick 143 32 Fig. 32. W~tinghouse: Last Style of Double-Bunon Carbon. Fig. 33. RCA Type 1 Double-Bunon Carbon. • • • • • Fig. 34. GE Experimental Conden~r Microphone. Fi&- 35. 1926 GE BuUet Microphone. 33 35 up anything in lhe background Hov.e\'er, lhe inside or the cylinder was lined with half-inch thick fdl. After a shor1 time or le as the Model 4A condenser microphone. [f purchased with the •announce• or desk stand, the model number was 4AA. If bought with the Door stand, it was the model 4AP (Fig. 37). Western Electric was the leader in microphone engineering and de velopmenl. As a subsidiary of the Americnn Telephone and Telegraph l4S 36 Fig. 36. GE Bullet Condenser, RC or 3A. Fig. 37. RCA 4AA Condenser Microphone. 38 Fig. 38. WE Nos. 373W, 387W, and 600A. Fig. 39. WE No. 371. 37 39 Company since 1882, having made telephones as early as 1878 for Western Union, WE was well qualified. Through these early years they made a wide variety of transmitter-microphones. After the 369-type double-button carbon, they made three more similar models for the broadcast industry: Nos. 373, 387 and 600A (Fig. 38). They also made two desk models for general use such as announcing. paging. and dispatching. These were the 371 and 389 (Fig. 39). In 1922 when AT&T put WBAY and WEAF on the air, it was trying to use the latest technology in all areas. This resulted in the trial use of their condenser microphone for broadcasting. This experimental model was quite large. The microphone element was mounted in the 146 lA bro112C housing. which sat atop a wooden plant )land. A short coaxfal cable connected to 1 floor-:.taoding Victrola cabinet. ¥rhich bouseJ the preamplifier> anJ battcrie:. (Fig. 40). lt *U inter~ling to note the station cngineo:c's log of August 10, 1922: *fiN Ul>e of con denser transmitter. Have been using carbon microphone up to now." August 16~ *First broadcasting Oller WEAF, W E. Co West St Tried condenser transmitter but it failed almost immediately. Resumed oo carbon mic. Programs from WBAY ~tudio: August 17: "WE.AF has trouble WBA Y starts up again 360 m. Condenser transmitter Sign off wi1h statement that WEAF is being used instead of WBA Y." Au gust 18: "Condenser mic. sounds 'wheezy.' Change to carbon." Au~st 23rd: "Condenser transmitter working fine. Sing [oscillatlon) elimi nated• September 14th: "Condenser microphone 'drips' - Intermit tent clicks We sig11 off for WJZ time signals." Sep1ember 21st: "Condenser trnnsmitter in trouble. Blew it out with hot air WEAF still using WBA Y studios." Fig. 40. Fir~t WE Condenser Microphone and Amplifier. Fig. 41 WE D-70837 Condenser Microphone and 0-80513 Amplifier. In 1925 a more compact version of this miaophooc wu produced and sold in some quantiiy. This was the D-80513 amplifier 11>ith the mi crophone clement mounted on top in the 1A housing. or spring suspen sion ring (Fia, 41 ). The amplifier box measured 8-1/4 inchu aquue by 5-1/4 inches high. It was lined with sheet metal for shieldina and con tained a one-tube preamplifier. A six-conductor cable brouaht power in and audio out. The microphone element was the new D-79897, later lO be given the number 394. In 1928, fh·e styles of oonbon Microphone. FiJ. 45. RCA 44A RJl>bon Microphone. 43 4S By 1931 Westinghouse and GE were out of the microphone business, leaving Western Electric: and RCA RCA had been manufacturing the 4A condenser microphone since 1929 and was now introducing the nl> bon velocity miaophonc. Western Electric: came out with the 618A dynamic:, and Brush introduced the crystal microphone. Electro-Voice entered the market in 1927, custom·building double-button carbon mi crophones. Miaophone.s were not generally available to radio ama· teurs, bands, or the general public, so small companies like Elec:tro Voice were beginning to appear aU over the country to satisfy the de mand. In the 1930s there were over 50 miaophone companies in the U.S.A. For this article I will continue only with RCA and WE, who t48 were supplying the microphones ror the broadcast and movie industries. The first microphone RCA made for the movie industry was the PB 17. The housing for this mlc was the Slime as some of the one-of-a kind GE condenser types. It was a s.indblasted aluminum cylindec 17 inches long and 6 inches in diameter The bottom was rounded, with a yoke to hold the ribbon element, which had a protective perforated screen. The mapietic structure u-ed an electromagJ1et requiring six volts at one ampere. The cylinder housed a three-tube preamplifier using 864s (Fig. 44). The fini RCA broadcast ribbon (Fig. 45) was the 44A Early units used electromagJ1ets; later production used three horseshoe permanent magnets. The 44A wu finished in antique bro112e. The 448 came out in the late I 930s, fini.hed in black and chrome. In the late 1940s the 44BX was diangcd in color for television to &\'Oid light glare. RCA called the new colors "TV" or ·umber" i!ey and satin chrome. The gray "''aS actually more of a dark beige, v.hile the 1Creens v.ere natural alu minum. Uolil nl>bon ~ came on the scene, microphones were omnidireci tiooal in their pu:kup patterns. This means they picked up sound from all directions, and were pressurc·opcrnted devices. However, most nominally omnidirectional microphones became relatively directional at higher frequencies. The ribbon microphone.~ were bidirectional They picked up sounds equally from front and rear, but lit tle from the sides, top or bottom. This was referred to as a figure-eight pattern. Ribbons are velocity or prcssurc-grudlent types, meaning that the sig nal voltage is proportional to particle velocity. In 1936 RCA introduced the 77A ribbon microphone (Fig. 46). This was the Cirsl unidirectional type. This microphone used two ribbons. One operated as a velocity and the other as a pressure type. Since the phase relation.ships of the two arc different, the resulting pickup pat· tern becomes cardioid or heart-shaped The lower part of this micro phone consists of a stack of i"OOved discs with lnmbs's wool in the grooves. The purpose of this design is to absorb the pressure behind the pc=e ribbon. A more steamlined version of this microphone was supplied 10 the movie industry, u the Ml-3043 or KU2A 'skunk mic' (Fig. 47). The nickname 'skunk" came from the colors all bbcl with a wide white stripe down one side of the ICl'cen for directing iL The RCA 77B was a smaller, more streamlined version of the n A. The nc (Fig. 48) looked identical to the •a• m:cpt for a ring·type switdi on the lower part of the miaophone. Thi. wu for selcaing the velocity n'bbon (figure-eight pattern): the pre»ure ribbon (omni pauern); or the com- 149 4 Fig. 46. RCA 77A. Fig. 47. RCA MI-3043 "Skunk." Fig. 48. RCA 77C. Fig. 49. RCA 74B. ' l .· IJ 48 50 Fig. 50. RCA 50A Inductor Microphone. Fig. 51. RCA 88A Dynamic. 150 47 49 51 I .. ea 53 Fig. 52. WE 630A with DircctionaJ B:iffle. Fig. 53. WE 633A 'Sall Shaker" Dynamic and SB Transmitter At tachment (Baflle). binalion of two (cardioid paucm). Lntcr technic::1l and color changes resulted in the 770 and 77DX. Physical appearance '1ayed the same. RCA produced other microphont:S during this period. The 74A and 74B were smnll versions of the 44·typc. Weij;htwise they were 2-1/2 pounds, compared to the 8-1/2 pound 44s. These were for less de manding applications, such as remote broadcasts. The 74A had a sim ple yoke and the finish wus brown wrinkle. The 748 was first black and chrome, then umber gruy und oluminum, wilh n swivel mount replacing the yoke (Fig 49). To compete with the Western Electric 618A, RCA produced the SOA (Fig. SO). This wns cnUed an inductor microphone. In reality it was a pressure type. Lnter came the 88A (Fig. SI), which was a moving-coil or dynamic type. A "bantam' velocity microphone, the KB-2C was introduced as 11 de~k microphone for general announc ing. This covers the RCA broadc:1st type microphones up to about 1950. Western Electric followed their 618A with the 630A ' eight-ball" (Fig.. 52). Then came the 632C. a clo>e-talk announce mic, a.nd the 633A "Rlt $baker" (Fig. SJ). In 1937 WE introduced the D-99098 tubular directional clement, wruch convened the 618A omnidirectional unit into a 'shotgun' or 'rifle• microphone. Thi.s desiJlTI (Fig. S4) was used for long-distance pickups. In 1938 ERPI (Electrical Research Products, Inc.), a divWoo of Western Electric ... 'Orking with the movie industry, produced a small condenser microphone. This .... u given the number D-99848. It used a new condenser clement with the model number 640A lt lookcd like a larie bullet, and had a black ....nnkle finish. 151 Fig. 54. WE 618A with D-99098 Directional Element. Fig. SS. WE 639A. 56 Fig. 56. WE RA 1142. 55 51 Fig. 57. WE 640AA Condenser Microphone and RA-1095 Amplifier. In 1939 WE introduced I.he 639A microphone. This was nicknamed the "bird cage." II was a rather large unit because it contained a ribbon and a dynamic element II had a three-position switch which selected the ribbon (bidirectional), the dynamic element (omnidirectional), or a combination of the IWO (unidirectional). The Inter 6398 (Fig. 55) con tained a six-position switch which allowed variations of these three pat· terns. ERPl supplied this same microphone in a different housing for the movie industry under the model number RA 1142 (Fig. 56). This housing was larger and made of perforated metal with a bail for boom use. The hist Western Electric broadcast microphone was the 640AA (Fig. 57) with the RA 1095 amplifier. lt looked very much like the 1938 movie condenser except for a chrome finish. This microphone was in· troduced in 1946 and aimed at the FM broadcast market. 152 Both RCA and Western Electric made a variery of other micro phones for non-broadcast use. WE sold its microphone and loud speaker line 10 Alice in 1949. Altec continued to make the 632C. 633A, 639A, and 6398 for a while and introduced its own condenser micro phone. the M 11 sy•tem, in 1949. RCA continued to make microphones up into the 19'70l but ~cntua.lly phased out of this business. There were other early companies that made broadcast microphones on a small scale, usuaUy condenser types. A shon list would be Brush, Bud. Carrier, Collins, Gates, Jenkins and Adair, and Remler. M05t of the companies that sinned around 1930 produced broadcast micro phones, but were unuble to penetrate the brondcnst market at that time. REFERENCES I. Dolbear, A E., ~Telephone (Boston: Lee & Shepard Publishers, 1877). 2. Presoon, G B., ~ Spe:.king Teleyhone, Talkina Phonograph. and QIW Ngychjg (New York: D. Appleton & Co., 18711). 3. Count du ~once!, ~ Telq?hone, '-ticrif1ph (New York Harper & Brothers Publishers. 1879). 4. Webb, H 1-. Ts:Js:phone Handbook (Chicago: electrician Publish· ing Co., 1907). 5. Goldsmith, A. N., &slli2 Telephony (New York: The Wireless Press Inc., 1918). 6. Wile, F. W., 1WJ.ik Berliner • Maker 1lf .Ifill Mjcrophone (Indianapolis~ Bobbs Merrill Co., 1926). 7. Rhodes, F. I,.., BtGinnjnlJ:S Qf Telephony (New York: Harper & Brothers Pub., 1929). 8. Fessenden. II. M., Fessenden • Builder 1lI TomoU0\111 (New York: Coward·McCann Pub., 1940). 9. U.S. PatenlJ 174,465; 186,787; 239,742; 246,512; lS0,126; 250,129; 250,2.SO; 406,567; 463,569; 48.5,311; 665,639; 824,1.59; 999,019; 1,068,871; 1,088,018; 1,117,231; 1,148,827; 1,237,933; 1,332,873; 1,333,744; 1,430,2.58; 1,432,885; 1,4S6,S38; 1,509,818; 1,527,649; 1,.5.57,3.56; 1,.569,41 l; 1,594,802; 1,611,870; 1,626,636; 1,626,645; 1,634,210; l,63S,S68; 1,636,785; L,637,397; 1,667,149; 1,678,842; 1,693,42.5; 1,722,347; 1,758,777; 1,766,463; 1,790,SOS; 1,795,874; 1,802,782; 1,847,702; 1,878,271; 1,885,001; 2,024,705; 2,22.5,312; Gray's Caveat, Feb. 14, 1886. IS3 Bob Paquette'• Microphone Mwieum ls a prlvatt collection slarle:d in 1950 and dispJayed since l970. It is th.e ttSult of a continuing resea.rdated with tni¢rophontt al\d lhtir use are also displayed. Thi!> includes many types o~ desk and floor stands, microphone enclosures, translormtrs, preampli(iers, amplifiers <11ncl test eq:u1p~nl . Or. filt is a coUcction of ~iHcation &htets. ~ttnt copi6, c.ait..Jog:s. ad,.,trtisirn> liter41twt, ttc:hni¢.ail raptr• and C<1-pii1:'$ Qf ~rUc::les that aJ)Ptar~ In eariy boob, masazlnes. and technkal perlodicati. Three di!>plays a.re set up to !how the servl« "

A Brief History of Microphones

Archive

Radio Alpha

Name/Title

Scope and Content

Category