Magnetic Recording

© Brooke Clarke 2022




Background
Description
Patents
Related
References
Links

Background

Since the Poulsen Magnetic Telegraphone was made to be a telephone answering machine this started out on the phones web page.  But as it grows in scope it needs a page of it's own.

For a number of years I played with a Magcord 1024 rack mount reel-to-reel tape recorder that came from an AM broadcast station.  It uses torque motors to tension the tape and control the feed and take-up reels.    The record and read heads are seperate so it's possible to overdub.  It has bias and equalization adjustments to allow peaking the recorder performance for the particular brand and model of tape.  I made many plots of frequency response with different settings to optimize the flatness.

Then discovered the idea that a high frequency audio signal on the input also acts as a recording bias signal.  So another way of setting up a recorder would be to use a number of simultaneous tones instead of a single frequency like what I was doing.  Maybe a more advanced method would be to use a flat white noise signal?

Prior to the use of AC for recording head bias and erasing a prior recording, Permenant Magnets were used for erasing in low cost wire and tape recorders.

I was involved with the HP/Agilent "E5022 Spin Stand" used to evaluate hard disk heads and media.  This is a practical application of quantum mechanics, i.e. the design of the heads and media.

Description

Early Magnetic Recording

It appears clear that Poulsen based his magnetic wire recorder on the Edison cylinder phonograph (Wiki).  The physical similarity is striking.

Poulsen

Museum of Magnetic Recording - Wire Recorders -
Wiki: Timeline of audio formats -

Poulsen
                      Magnetic Telegraphone - Wire Recroder
From the Telegraphone Wiki page.

The Telegraphone was one of if not the first magnetic recording device invented by Valdemar Poulsen (Wiki) in 1900 long after the Edison Cylinder and about the same time as the flat disk record.

Minifon

While watching the movie Dragnet (1954, Wiki, IMDB) an undercover policewomen "wears a wire", i.e. is using a wire recorder.  (not that there's a wire from the microphone).
https://www.reddit.com/r/etymology/comments/gqp6cy/where_does_the_term_wearing_a_wire_come_from/
Meaning she has a hidden Model 51 Minifon wire recorder (Wiki).  Not the P55 or Ng55D because the recorder in Dragnet did not have the classic Stop, Rewind, Play Back and Record buttons, i.e. it was the wire version.

Model 51 Minifon wire recorder
Photo from Wiki: Minifon

This is the Minifon Model 51 wire recorder in the movie Dragnet, 1954.

PS In modern (2022) movies people talk about looking at the (video) tape.  Yet the recorded images are coming from a hard drive.  This is a reference to the prior art called video tape such as VHS tape (Wiki).

PS The attaché model, with the tape cassette like push buttons is actually a cassette tape recorder called the P55.
The P55 tape recorder is used very near the end of the 1958 movie Touch of Evil (Wiki, IMDb) along with a home built tube type wireless mike (Wiki).
3134074 Microphone transmitter having a lavalier type antenna, Ray A Litke, Vega Electronics, 1961-05-08, - not the first wireless mike, but first patent - transistors

Webcor

Webster-Chicago (Wiki) made record changers, wire recorders and reel to reel tape recorders.  Maybe it's a concidence that Armour Research Foundation (Wiki: IIT Research Institute) is also located in Chicago and Armour Research Foundation holds many early magnetic (both wire and tape) recorder patnets.

Patents

Patent Classes:
Class 360: Dynamic Magnetic Information Storage or Retrieval

Magnetic Recording Patents

227679
                              Phonograph, T. A. Edison, 1880-05-18
227679
                              Phonograph, T. A. Edison, 1880-05-18

227679 Phonograph, T. A. Edison, 1880-05-18, 369/214; 116/144; 181/162 -

A cylinder has a helical groove that wiggles up and down to record sound.

The Poulsen device is a cylinder with a helical wire that magnetically records sound.
661619 Method of
                      recording and reproducing sounds or signals,
                      Valdemar Poulsen, 1900-11-13
661619 Method of recording and reproducing sounds or signals, Valdemar Poulsen, 1900-11-13, 360/87; 235/449; 379/70; 360/136 -
Although the patent does not use the words, one of the applications is as a telephone answering machine, hence "Telegraphone".

Poulsen probably had seen images of the Edison Cylinder machine if not a real one in action since it had been around for a decade.
His idea duplicates the Edison Cylinder except instead of cutting grooves in wax Poulsen is magnetizing a wire would around a cylinder.  This is for all intents and purposes a wire recorder (Wiki) but with a much shorter wire wound on a cylinder.
773985 Apparatus
                      for recording and reproducing speech, Elias E
                      Ries, 1904-11-01
773985 Apparatus for recording and reproducing speech, Elias E Ries, 1904-11-01, - wire recorder
788728 Apparatus
                      for electromagnetically receiving, recording,
                      reproducing, and distributing articulate speech,
                      &c., Valdemar Poulsen,1905-05-02
788728 Apparatus for electromagnetically receiving, recording, reproducing, and distributing articulate speech, &c., Valdemar Poulsen,1905-05-02, 360/7 - steel wire (a) loop moved by pulleys.
873078
                      Electromagnet for telegraphone purposes, Peder
                      Olof Pedersen,Valdemar Poulsen, American Telegraph
                      Co, 1907-12-10
873078 Electromagnet for telegraphone purposes, Peder Olof Pedersen,Valdemar Poulsen, American Telegraph Co, 1907-12-10, 360/125.01 -  This is probably the first magnetic recording head.  But it has a lot of room for improvement.

900304
                      Electromagnet for telegraphones, Peder Olof
                      Pedersen,Valdemar Poulsen, American Telegraph
                      Co,1908-10-06
900304 Electromagnet for telegraphones, Peder Olof Pedersen,Valdemar Poulsen, American Telegraph Co,1908-10-06, 360/123.01 -

While not much improvement in the recording head, Fig 5 does show the steel wire on a spool, so now looking like a reel to reel  wire recorder.

Now all that's needed to me more modern is a horseshoe core with a very narrow gap on the recording head.
1237496
                      Telegraphone, Charles K Fankhauser, Arthur M
                      McCrillis, 1917-08-21
1237496 Telegraphone, Charles K Fankhauser, Arthur M McCrillis, 1917-08-21, - wire recorder, Pointer (83) and dial (84) indicate the percentage of wire used by indicating the radius of the spool.

1560721
                      Automatic reel-stopping device for
                      record-o-phones, Hugh P O'reilly, Record-O-Phone,
                      1925-11-10
1560721 Automatic reel-stopping device for record-o-phones, Hugh P O'reilly, Record-O-Phone, 1925-11-10, -
Emerson Record-O-Phone Telegraphone (see: Museum of Magnetic recording\Wire Recording) for photos

2245286 Electromagnetic sound recording, Marzocchi Luigi, Priority: Jun 26, 1936, Pub: Jun 10, 1941, 360/84, 369/97, 360/83, 346/139.00A, 360/122 - scanned mag tape recording   referenced by 91 patents

2306162 Sound device, Harrison S Gipe, App: 1940-08-08, W.W.II, Pub: 1942-12-22, 360/89; 242/324.3; 360/75 - suitcase size, talks about problems with both tape and wire media.

D149541 Wire Recorder, Colin B Dale, Webster-Chicago, 1948-05-11, - Model 80 portable design

2364556 Telegraphone, Richard M Somers, Thomas A Edison Inc, 1944-12-05, - cassette with built-in recording head and multi-track tape that auto sequences and auto-reverses, like for dictation.

2351011 Method of and means for energizing magnetic recorder heads, Camras Marvin, Armour Research, 1944-06-13, - includes oscillator (18) "...Also an object of the invention resides in the provision of an electrical circuit arrangement for a magnetic recording device in which the output of an oscillatory hook-up is divided into a plurality of parts connected in series, one of the parts functioning as an erasing head to recondition the previously magnetized recording medium, and another part being directly associated with the recording head of the device to set up a high frequency magnetic field in the recording head." 

2369017 Magnetic recorder and drive therefor, Camras Marvin, Armour Research Foundation, App: 1943-02-25, W.W.II, Pub: 1945-02-06, -

2351005 Magnetic recorder, Camras Marvin, Armour Research, App: 1942-07-27, W.W.II, Pub: 1944-06-13, 360/89; 242/324.3 - Wire (or tape), Introduces the need for a bias oscillator (Fig 7).

2416610 Magnetic recorder utilizing an energizing oscillating circuit, Camras Marvin, Raymond E Zenner, Armour Research, App: 1942-12-26, W.W.II, Pub: 1947-02-25, - wire recorder, mostly about small size for use on aircraft AIC circuits, "...such an oscillating circuit is understood by those skilled in the art. " So the bias oscillator came earlier.

2461368 Magnetic transducing apparatus utilizing a helical sound trace, William E Bradiey, Philco Corp, Filed: Dec 19, 1944, Pub: Feb 8, 1949, 360/29 - wire recorder.  They had problems with wire rotation.

2466514 Magnetic recording and reproducing device with means to prevent accidental erase of record medium, Harold A Vagtborg, Armour Research Foundation, App: 1944-11-23, SECRET, Pub: 1949-04-05, - Spool interlock to prevent overwriting.

2475421 Combined erasing and recording magnetic transducer, Camras Marvin, Armour Research, 1949-07-05, - "E" core head with seperate gaps and windings for Erase and Record/Play.  Both 2 and 3 gap versions (erase, record, play).

2481004 Wire recorder, Colin B Dale, Webster-Chicago, 1949-09-06, 242/324.1 - wire tension control

2493657 Method of winding wire onto a spool, Colin B Dale, Webster-Chicago, 1949-09-06, 1950-01-03, - the spools move up & down to spread the wire evenly.

2499699 Wire and tape driving means, Russell J Tinkham, Magnecord, 1950-03-07, - without using sprocket holes - capstan drive shaft (13) is hard, pinch rollers (14 & 15) are soft.

2532541 Mounting for wire recorder supply spools, Colin B Dale, Webster-Chicago, 1950-12-05, - the spools move up & down to spread the wire evenly.

2536126 Wire recorder spool, Colin B Dale, Webster-Chicago, 1951-01-02, - with pinch to hold end of wire.

2537260 Wire recorder, Colin B Dale, WebsterChicago, 1951-01-09, - maybe Model 80 portable, Classic Play - Stop - Rewind lever at front of deck.

2540654 Data storage system, Arnold A Cohen, William R Keye, Charles B Tompkins, Engineering Research Assoc, 1951-02-06, -
Cites IBM punch cards (2150256) as prior art, Cited by 200 patents! i.e. pioneer digital magnetic recording

2596536 Wire recorder, Colin B Dale, Webster-Chicago, 1952-05-13, - Nylon or string leader on end of wire

2614845 Wire recorder, Colin B Dale, Webster-Chicago,1952-10-21, - maybe to keep the wire from spilling

2616982 Magnetic recorder, Gray Robert, Ellis Robert, Raytheon, App:1946-08-24, SECRET, Pub: 1952-11-04, - small size, reliable, easy to use; why, for spies? or use on military vehicle?

2692379 Blocking oscillator magnetic recording device, Dolan H Toth, Sec of Navy, 1954-10-19, 360/67; G9B/5.05; G9B/5.033; 346/33M - for digital data, correct closed loop head design with small gap, the recording head is also the transformer of the blocking oscillator (also see Joule Thief).

2698875 Plural track magnetic recording and/or reproducing apparatus, James H Greenwood, Magnecord, 1955-01-04, - 6 tracks - "One application of the invention is in the field of recording television (video) signals for subsequent reproduction. Another application of the invention is in the field of recording military and communication signal currents of a frequency both within the standard video band as well as of frequencies above that band which are considered as falling within the video frequency range."

2713618 Pocket recorder, Louis A McNabb, 1955-07-19, - wire recorder, coaxial spools, dual coil "C" shape read/write head, Record-Off-Rewind-Off-Listen switch,

2778636 Endless tape cartridge, George H Eash, Charles I. Poulsen, 1957-01-22, - Wiki: 8-track tape -

2796571 Electric motor, William L Dunn, Magnecord, 1957-06-18, - "... single-phase alternating-current machine that can be used as a synchronous motor, a variable speed motor, or a variable speed motor synchronized by external Synchronizing pulses." i.e. a stepper motor

2819957 Steel alloys for making magnetic recordings, Appel Karl, C Pouplier Jr, 1958-01-14, - patent number seen on a Protona minifon P55 wire reel - Example 6: "This alloy is made into a wire having a diameter of 0.05 mms. Coercive force 450 oersted, retentivity 3000 gauss, at field intensity 900 oersted. "

2956114 Broad band magnetic tape system and method, Charles E Anderson, Ray M Dolby, Charles P Ginsburg, Jr Shelby F Henderson, Ampex, Oct 11, 1960, 360/30, 386/E05.9, 386/335 - helical scan video  

3016244 Miniature magnetic sound recording and reproducing device, Schuh Carl Friedrich, Bavaria Lower, Hermann Gunter, Protona Prod, 1962-01-09, - Was this the start of the piano keyboard push buttons that were used on cassette tape players, i.e. Stop, Rewind, Play Back, Record?  The P55 model.  The model in Dragnet 1954 movie was an earlier M55 version.




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References


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Page Created 2022 May 7