The Early Years of Teletype Development
A Patent History
Ransom D. Slayton, Consultant
1983?
(Document Notes)
1901 - The Beginnings
The initial event in the chain of circumstances that led to
the successful development of Teletype printing telegraph systems was
the appearance in Chicago of young Frank D. Pearne, originally from
Nebraska. He had come to enlist support for his "inventions." An
article published in the Sunday Feature Section of the Chicago Tribune
dated March 3, 1901 gives a brief sketch of Pearne's history and ideas.
(A photocpy of the article was sent to Teletype Museum storage.)
Pearne apparently had two objectives: (1) to provide remote
operation for a Mergenthaler typesetting machine, for the newspaper
field; (2) to get direct printed copy, for the telegraph field. Some
of his equipment, described in the story as having been made in Chicago
and Syracuse, New York is shown in a picture accompanying the article.
Apparent are: (1) A keyboard sender which the inventor is
operating, specially designed, it seems, to provide separate electrical
circuits attached to each key; (2) A distributing device, or selector,
consisting of large polar relays, shown at the front; (3) A set of
intermediate relays, entitled "switches," that were mounted to the
side of the typing unit which they controlled; (4) A modified magnet-
controlled typewriter (apparnetly a Remington No. 6) used as the typing
unit.
In the article Pearne claims that his sending principle uses
electrical currents of different combinations of polarity and strength
for the determination of individual characters to be transmitted and
received. This method is spelled out in detail in Patent No. 894,044
which he filed in 1904 and was granted in 1908. (See page 4.)
Frank Pearne was able to interest Mr. Joy Morton of the
Morton Salt Company in his work, and he secured a limited amount of
financial support. He was given working space in the attic of Mark
Morton's Western Cold Storage plant office (Mark was Joy's brother),
and Charles Krum, Vice-President of the Cold Storage Company, a trained
mechanical engineer experienced in the design of mechanisms, was
enlisted to provide practical guidance. This apparently happened in 1901,
since the first record of the association of Pearne and Krum is a patent
filing made early the next year.
1902 - Krum and Pearne Joint Developments
On February 3rd, Peirce and Fisher, attorneys, who subsequently
represented Frank Pearne, Charles and Howard Krum, and the Morkrum
Company in most of their patent work, filed a patent application on an
"Electrical Sensitive Apparatus" in the name of both Pearne and Krum.
This patent was issued on March 15, 1904 as No. 754,689* and was assigned
to the "Pearne Electric and Manufacturing Company" of Chicago, which was
apparently the corporate entity set up by Morton and Pearne to support
the work then underway. The patent itself covered a relay having
a locking feature which could be set into two or three different
positions, to be used to control signals from a main telegraph circuit
to two or three branch circuits for signaling and for controlling
separate parts of a printing telegraph set or an electrical typewriter.
This type of circuit formed the basis for early Pearne and
Krum selectors by the way in which it set up paths to typing unit control
magnets. (Patent No. 888,335, to Charles Krum, shows five of these
relays in its Figure 29 -- see page 3.) The relay itself was a two-
or three-position device with two branch outputs having locking magnets
for each of the side outputs and means for releasing the lock.
Thirteen claims were granted. Two models are in the Teletype Museum
storage.
Another device on which Pearne and Krum cooperated at about
this time was a keyboard transmitter unit. One Model has survived and
is in Museum storage. It is marked "THE KRUM-PEARNE TELEGRATYPE" and
"Patents Applied For." No patents have been found covering the keylever
and codebar arrangement of this unit. It may be that this part
of the unit was not an improvement over the prior art. A transmitting
relay bank was mounted behind the keyboard, and its circuitry and
components are described in Patent No. 929,603 (Page 6). It thus appears
that the keyboard served as a model for testing circuitry ideas, and
that the assembly was later "worked over" to include the relay bank.
The keyboard itself is a four-row instrument with each key
operating a linkage mechanism which selects a code pattern through a
group of U-shaped code bars. The code bars in turn control the closing
of corresponding telegraph signal transmitting contacts. A locking
magnet, claimed in Patent 929,602 (Page 4), held the contacts in position
during the transmitting interval. (This feature may not have
been claimed in the original patent applications on the TELEGRATYPE.
It also may be that the word TELEGRATYPE ws the inspiration of the
name TELETYPE when the latter was submitted in a contest to rename the
Morkrum-Kleinschmidt Company several years later.)
The frame of the device consists of carefully designed castings
but the levers and bars are somewhat flimsy. The code bars have
been reinforced by soldering on flat metal strips, indicating an attempt
at solving the weakness.
Sometime during this early period, Frank Pearne lost interest
in the work, going off to teach at the Armour INstitute of Technology
(now IIT) and his association with Charles Krum was severed. Krum
continued, however, and within a few years had made such progress that
a separate corporation, the Morkrum Company, was formed to develop and
produce printing telegraph products.
1903 - Krum Continues Alone
The first recorded patent granted solely to Charles Krum was
filed January 10th and issued February 5, 1907 as No. 843,283. This
was an "Electrical Signal," a telephone style ringer which used a
permanent magnet for bias and an electromagnet for operation. It worked
on square wave AC signals which were applied to the electromagnet coil.
This method was claimed to be suitable for party line telephone ringing.
While not used in the telegraph art, it demonstrated Charles Krum's
interest and rapidly developing ability in the electrical design field.
Six claims were granted.
On August 22nd Charles Krum filed an application that covered
a "Printing Telegraph." As Patent No. 888,335 it was issued on May
19, 1908. This covered a keyboard sending, typebar receiving style of
printer, with the printer design closely related to that of a conven-
tional typewriter. Individual magnets were used to operate the typing
keylevers when receiving copy, and solenoids or magnets supplied power
for character spacing and line feed. Carriage return was magnet tripped,
with spring power providing the return itself. The spacing mechanism
was locked out during the return interval and then reactivated at the
end of the carriage travel.
The shock of stopping the carriage was cushioned by "dash
pots", and it was stated that this was a preferred method. Ribbon feed
was incorporated into the mechanism. The ribbon shifted to follow
carriage shift in printing any of three cases of characters. (Many of the
typewriters of that day had three different cases: CAPITALS, FIGURES
and LOWER case.) Copy was made visible for the printer operator by
having the ribbon move out of the way between typing operations.
Carriage shift occurred with each CAPITALS or FIGURES character, and
unshifting occurred immediately. (The use of separate code permutations
for SHIFTing and UNSHIFTing was a later development.)
In the keyboard the key levers controlled circuit closures,
directly energizing typing unit selecting relays and sending-to-line
relays. At the bottom of each key stroke, a universal-bar circuit
provided a lockout so that transmission did not reoccur on the key
return stroke. The signaling code was similar to the Pearne code, with
each pulse having one of two strengths and one of two polarities. The
Pearne-Krum relay, Patent No. 754,689 is shown in the circuit diagram.
The 16 claims cover the carriage and ribbon shifting, the ribbon feed,
the carriage return, and the line feed functions, all of which had been
problems when trying to use a typewriter as a telegraph printer. The
keyboard is much simpler than the TELEGRATYPE and apparently incorporates
improvements gained by experience with the latter. No model has been
preserved.
1904 - Separate Krum and Pearne Applications
The first of three telegraph patent applications during this
year was filed by Charles Krum on April 11th. It issued July 27, 1909
as No. 929,602 and covered a "Transmitter for Electric Telegraph." It
consisted of a keyboard transmitter, much simpler than the TELEGRATYPE,
which used relay distributing chains for transmission. The operation
of each finger key set up electrical circuits for sending trains of
pulses, with the circuits locked in until the transmission was finished.
Each train could be of several types (in "any suitable code"),
according to the specification.
For example, in the original Pearne system, which was closely
related to the French Baudot, each train consisted of pulses separated
by no-current intervals, the pulses themselves having either
one of two polarities and either one of two strengths within those
polarities. In this application, Krum states that in addition to the
above, the pulses may also be of variable time duration, as in Morse,
or that the pulses may be prolonged to the point of having no gaps between
them. A finger key, once operated, was free to prepare to set up the
next character, but all others were locked out until the previous
character had been transmitted. (This feature was included in the
TELEGRATYPE).
If a key was held down, it caused the transmission of repeated
characters until released. If two or more character keys were held
down simultaneously it appears that an error could be sent. Further
improvements over the mechanism shown in Patent No. 888,335 are
apparent. The 49 claims granted cover the transmitting relays, the
keys and contacts, and the locking mechanism. No model has been
preserved.
On July 11th, Frank Pearne filed on his original signaling
ideas, assigning the device to a Mr. M. E. Stewart of Chicago, who
apparently was financing him at that time. This Patent issued July 21,
1908 as No. 894,044. The title was "Electrical Selective System,"
and covered the relay network used by Pearne for generating and
receiving signals. The signals themselves consisted of trains of pulses
with intervals of no-signal between the individual pulses. Each
pulse was either of positive or negative polarity, and of greater or
lesser strength. With three successive pulses, each able to be put
in one of four signaling conditions, 64 code combinations signifying 64
individual characters or operations could be established.
The claims cofer a combination of line circuits and branch
circuits, with switches (relay chains) controlling sequential operation
of the branch circuits for transmission or reception. At the end of
each pulse transmission, the system connections were transferred
to the next condition. A reset occurred at the end of each pulse train.
The first of five pulses started the selecting process, while
the second, third, and fourth pulses caused the actual selection.
The fifth pulse completed the operating, started the printing cycle
at the receiving terminal, and brought about the resetting of all
circuits at both terminals to the idle condition.
Weaknesses of the design were: (1) Two current levels of
different polarities had to be detected which was difficult on "open
wire" lines subject to current fluctuations with variations in the
weather; (2) The relay chains could not provide precise timing of
transmitted and received trains of signals. The single current
START-STOP system invented by Howard Krum overcame the first problem,
and motor driven distributors which were eventually developed solved
the second. This patent covers Pearne's early work, and the equipment
described is similar to that shown int he Tribune picture of
March 3, 1901. Charles Krum used related signaling principles until
the START-STOP system was invented but deliberately did not make any
claims in this particular area. Pearne was granted 35 claims on the
selective system.
On October 6th, Charles Krum filed on a "Printing Telegraph,"
which Patent was subsequently issued on August 6, 1907 as No. 862,402.
This covered a solenoid powered typewheel page printer with the
typewheel mounted on a horizontal axis. The wheel was to move back
and forth horizontally, and also rotate about its axis, in order
to select the various characters for printing. Selections were made
through the positioning of stops which prevented the wheel from moving
or rotating further. The wheel and an associated ribbon were located
in front of the paper for visibility of copy. A hammer with magnet
drive was located behind the paper.
Printing occurred on a "print through" basis as in the Hammond
typewriter which was in current use at that time. The drive
magnet started the hammer on its printing stroke, but completion of
the stroke was by intertia after the electrical power had been expended.
The hammer opened a contact at the end of its stroke, resetting
the electrical circuitrty and preparing the mechanism to receive the
next character. The received signal is the three-impulse, four
current condition of the Pearne selector (Patent No. 894,044), and
specific selecting circuits are not claimed. The signal source for
printer oepration may have been the TELEGRATYPE keyboard or one of
its successors.
32 claims were granted, covering the typing mechanism and
control circuits. No model has been found of the printing mechanism,
but a model of a relay bank selector of about this date with
connections almost as shown in the patent has been preserved. Some
relays in this bank are of the same design as those mounted behind
the TELEGRATYPE.
Charles Krum continued his work during the next year, gradually
putting together the elements required to provide a practical printing
telegraph system that could be marketed.
1906 - Howard Krum Joins Charles Krum
On August 31st, Charles Krum filed on a "Transmitter for
Automatic Telegraph," which was issued as Patent No. 929,603 on July
27, 1909. This was a keyboard transmitter that used relay distributing
chains and which was controlled from a typewriter-like keyboard.
Cooperation with a receiving printer or typewriter having three cases
of type is indicated. Operation of each finger key moved code bars
and contacts to send a train of three pulses, each being in one of
the usual four conditions of polarity and strength. A magnet held
the keylever locked up until character transmission was completed.
Meanwhile all other key levers were locked out.
Case shifting, instead of being "on-the-fly" with the
transmission and reception of each CAPITAL or FIGURES character, was
now by manipulation of one of two separate keys which was held
depressed while sending in that particular case. This caused the
sending of a special SHIFT code when the key was first depressed and
of a different UNSHIFT code when the key was released. 58 claims were
allowed. No model of the keyboard design shown in the patent spec-
ification has been preserved, but a model of the transmitting relay
bank is mounted at the rear of the TELEGRATYPE keyboard in museum
storage.
Howard Krum graduated from the Armour Institute of Technology
that year and was employed during the summer to undertake field
testing of a set employing many of the principles described above.
The first test was on the Chicago and Alton Railroad between Chicago
and Bloomington, Illinois. While a successful demonstration was
accomplished, it was realized that many deficiencies remained in the
equipment, so Howard went to work full-time with his father Charles
to see if these could be overcome.
On September 6th, Charles Krum filed on a "Printing Telegraph."
This was issued as Patent No. 1,004,038 on September 26, 1911. It
consisted of the relay circuits that were being used to decode the
complicated line signals so that a signle magnet would be selected
for each chacter sent. In turn, the magnet would cause the selection
of the proper typebar lever in the associated typewriter printer, causing
the printing of the letter. 30 claims were allowed.
1907 - Morkrum Company Founded
A year's work produced results that were promising enough to
justify formation of a manufacturing company. The Morkrum Company was
accordingly founded on October 5, being chartered in the State of
Maine. The new firm took over the patents previously issued, as well
as rights to applications being processed for Charles Krum. The Morton
family provided the major part of the financing, with joy Morton,
Mark Morton, Sterling Morton, Charles Krum, and Daniel Peterkin, Sr.,
all having interests. (The name MORKRUM was derived from MORton and
KRUM.) Work continued on new developments.
1908 - The Krums at Work
An application was filed jointly by Charles and Howard Krum
on January 22nd covering a "Printing Telegraph." This applicaton
was renewed on February 14, 1916 and issued on September 19, 1916 as
Patent No. 1,199,011. It covered the controlling relay bank for the
first printing telegraph set developed by the Krums, a set that operated
in conjunction with an OLIVER typewriter through an adapter unit
from Patent No. 1,137,146, to be described later. The relays were
used for both sending and receving, and the line signal consisted of
five successive line current impulses of either positive or negative
polarity (MARK or SPACE) with no-current intervals between the pulses.
Distributing relay chains formed or followed the pulses, as
was appropriate for transmission or reception, and storage relays held
received permutations. When all pulses had been detected at the
receiver, the permutation was transferred to a "fan" or "Christmas
tree" decoding network, and one of the 32 printer control magnets was
energized. (This was covered by Patent No. 1,004,038 described above.)
The printing operation or other function was then accomplished under
the control of strong power magnets within the typewriter. Functions
included either of two SHIFTS, UNSHIFT, CARRIAGE RETURN and LINE FEED.
Operaton was on a "overlap" basis with a printing or operating function
being performed as the subsequent character was being received.
The patent specification shows a Krum relay, Patent No. 1,172,294
(described below) connecting the receiving line to the set; this was
the only polar relay used. The printer drive circuitry and the keyboard
sending circuitry were from patent 1,137,146. Operation of either
SHIFT key injected a special signal, following which either the CAPITALS
or FIGURES case characters were sent and recorded until the key was
released. A RELEASE (UNSHIFT) was then inserted, and subsequent
printing was in LOWER CASE letters. This feature was covered in
Patent 929,603. The 55 claims granted covered distribution of signals,
selection of signals, storage, and the overlap principle. Two models
have been preserved. Relays from Patent No. 1,220,433 (described
below) were used throughout.
On June 1st, Charles Krum filed an application on the polar
relay mentioned above. This patent, entitled "Relay", was issued
February 22, 1916 as No. 1,172,294, and covered a relay using a polarizing
winding instead of a conventional permanent magnet. The relay operated
on either polar or neutral input signals, and was claimed to be easily
manufactured and adjusted. 30 claims were allowed.
On the same date Charles and Howard Krum filed an joint
application for another type of relay called an "Electromagnet." This
application was renewed on August 18, 1916 and issued as Patent No.
1,220,433 on March 27, 1917. The device was a neutral relay of special
design, both rugged and sensitive, which could be cheaply manufactured
with common tools. Ten claims were allowed. It was the only
kind of relay used in the relay bank covered in Patent No. 1,199,011
for the first complete Krum printer set. It was used extensively
thereafter, especially in the GREEN CODE and BLUE CODE printer sets.
1909 - The OLIVER and BLUE CODE Printers
On February 4th, Charles Krum filed on a "Printing Telegraph
Apparatus," covering an adapter unit for controlling an OLIVER
or other typewriter. This Patent was issued on April 27, 1915 as No.
1,137,146. The adapter unit included code bars for operating trans-
mitting code contacts (same code as used in Patents 929,602 and 929,603)
and included receiving magnets for operating the key-typebars for
printing both sent and received copy. The double-shift typewriter
principle, described in Patent 929,603 was utilized. In the patent
specification, a good discussion was given of the problems encountered
in coupling into the functions: LINE FEED, character SPACING, and
CARRIAGE RETURN. The associated relay controls were covered by Patent
No. 1,199,011. 31 claims were allowed. One model has been preserved,
attached to an OLIVER typewriter with a special base casting.
On November 29th, Charles and Howard Krum filed on a "Selective
Telegraph System and Apparatus," covering a magnet- and solenoid-powered
typewheel page printer and associated keyboard transmitter. Patent No.
1,232,045 was subsequently issued on July 3, 1917 and a subdivision
was refiled on June 19, 1917, issuing as Patent No. 1,305,225 on May
27, 1919. This was the first successful typewheel Page Printer
designed by the Krums for telegraph service, and became the so-called
BLUE CODE and GREEN CODE printers of subsequent years.
Originally the typewheel contained three rows of type, for
the three cases: CAPITALS, FIGURES and LOWER. Later models had only
two rows, dispensing with the LOWER case. The typewheel was mounted
on a vertical axis and was rotated by magnet power to the right or
left in accordance with the polarity of the fifth pulse of the code
used. Its rotation was blocked by stops which were selected by the
first four pulses of the code. On encountering the closest stop, the
typewheel was roughly in position for printing the selected character.
A "corrector" (notched wheel) similar to that on a Blickensderfer
typewriter of the same vintage (models in storage) provided exact align-
ment of the printed characters during the printing process.
Printing was accomplished by swinging the typewheel to the
rear against the paper and platen as in the Blickensderfer, one model
of which had an electric motor and was thus the first electric type-
writer known to be in use. the wheel face was rubbed against an inked
felt roller enroute to the paper, thereby providing ink for printing,
the same as in the typewriter. A spring returned the wheel to the
neutral position after the printing was finished. Stops were inserted
momentarily for quick completion of the resetting operation. Magnets
lifted the wheel to one or the other of the SHIFTed positions and locked
it in that position until a release to the UNSHIFTed position was
required.
The wheel was mounted on a carriage that progressed across
the page in column SPACE order and returned to the left margin upon
receipt of the CARRIAGE RETURN signal. The machine was thus a "fixed
paper" type, with a minimum of paper feeding problems. Signaling,
selecting and control magnets were mounted within the machine, and
the circuit was described as an improvement over the original printer
bank, Patent No. 1,199,011, and its successor, Patent No. 1,286,351
which first used the START-STOP principle.
In the present instance, the line signal consisted of five
successive code pulses, without gaps between pulses, and slow-operating
relays were used to time individual pulse transmissions. A similar
relay chain operated in synchronism with received signals,
while quick-acting relays "sampled" the center of the received pulses.
The keyboard was largely covered by patent No. 929,603. 35
claims covered the typewheel print mechanism, the carriage, and related
functions. The stored model is a GREEN CODE version, with two
rows of type on the typewheel. It has "slip connections" for attachment
to a table set, and does not include a keyboard.
The split-off from the previous patent, issued as No. 1,305,225
on May 27, 1919 was entitled "Printing Telegraph." It covered a
variation of the typing unit wherein there was division between
the selecting and printer controlling circuitry which permitted
"overlap." The earlier unit operated to print a received character
and then was reset before the next character was applied. The new
unit allowed the printing of one character simultaneously with the
reception of the next character, obviously a much faster procedure.
Eight claims were allowed.
1910 - The START-STOP Principle
On May 31st, Howard Krum filed his basic patent on the
START-STOP telegraph signaling system. This application was renewed
on February 11, 1918 and issued as Patent No. 1,286,351 on December
3, 1918. Entitled "Electric Selective System," the patent covers a
relay bank that is similar to Patent No. 1,199,011 but has the new
START-STOP line signal arrangement. The relay bank was used for both
sending and receiving and in the latter case made sleections near the
mid-point of each of the line signal impulses. It was stated that
this process overcame the problems of line current variations and
disturbances, especially those due to changing weather conditions.
One problem encountered was that of "tuning" the various distributing
relays so as to maintain synchronism of the distributing chains.
(Motor driven "cam-and-contact" or "burhs-and-segment" distributors
solved that problem later.)
The keyboard shown in the patent is from Patent No. 1,232,045
and the receiving printer is the OLIVER typewriter shown in Patent
No. 1,137.146. The 38 claims cover the START-STOP principle.
They state that the transmitter is independent of the line conditions
and that the receiving selector, once started in response to a START
signal runs independently of the received signals until the STOP signal
is detected. Two models have been preserved. The relays are all
designed per Patent No. 1,220,433. Tapped holes in the relay mounting
plate indicate that the relay banks were originally per patent
No. 1,199,011 and subsequently were worked over to include the START-
STOP principle.
With basic patent coverage in process, the krums were now
able to produce complete and practical printing telegraph sets for the
communications field. The first set, called a BLUE CODE, was developed
for teh Postal Telegraph Company and sold to them this year.
Postal messenger boys' uniforms, telegraph blank headings and apparatus
were all colored blue, so the color code was a natural selection. A
GREEN CODE set with olive drab color was likewise developed for the
Western Union Telegraph Company, and was named for the same reason.
The sets had most features in common, differing only in minor details.
1912 - The First Keyboard Perforator
On June 18th, Charles and Howard Krum filed on an "Apparatus
for Forming Telegraph Tape" which was the first keyboard perforator
made by the Morkrum Colmpany. Patent No. 1,174,427 was issued on
March 7, 1916 covering this unit. In the perforator, each keylever
selected a combination of code bars, to each of which a contact was
attached. The contacts in turn energized solenoids which controlled
interponents between a solenoid-driven hammer and a set of punch
pins. Operation was "upside down" in that a selected magnet withdrew
its interponent from engagement with its punch pin so that no hole
was punched. Unselected magnets left their interponents unmoved,
with consequent hole perforation. Tape stepping was by pawl and ratchet.
The punched holes were at a slight diagonal, as aligned across
the tape, with a feed hole in line with the center line of the cod
holes.
The intent was to move the tape at a constant speed during
subsequent sensing, rather than to make a quick move and then leave
the state stationary during sensing. This is the so-called "drag-
reading" principle. the punch block had spring return of the selected
punch pins via a "stripper plate." The magnets were included so that
the unit could also serve as a reperforator on signals received from a
distant source. 15 claims were allowed. This is the first patent
application filed after the legal firm had become Fisher and Clapp.
The museu model in storage has an interesting addition
not covered in the patent specification or drawings: an inking roller
is attached to the CARRIAGE RETURN key and marks the tape with an
ink smudge whenever the key is depressed. This mark appears about
seven inches before that point on the tape reaches the punch block.
It apparently serves as a crude character counter to help the operator
prepare tape for transmission to a page printer that types a 72
character line. An apparent weakness is that the operator had to
keep moving his (or her) gaze between the tape and the copy being
read. (The successor perforator, the GPE, was designed with an END-
OF-LINE counter mechanism and warning lamp.)
1914 - The GREEN CODE Perforator
On September 8th, Charles and Howard Krum filed an application
on a "Perforator for Forming Telegraphic Tape." The Patent was issued
May 9, 1916 as No. 1,182,179. This is the GREEN CODE PERFORATOR
(GPE) in its final form of which 6173 units were to be made and sold
over an interval of some 50 years! Keylevers operated groups of code
bars, extensions of which pulled bell-cranks linked to interponents that
moved in and out between the solenoid-driven hammer and the punch pins.
This eliminated the contacts and solenoids found in Patent No. 1,174,427
and made for a simple, rugged unit. A back-space mechanism, and an end-
of-line indicator lamp were added.
A horizontally mounted supply tape holder turntable was
included on top of the keyboard assembly, with a spring loaded tension
arm buffering the stripping of blank tape from the roll on its way to
a simplified feed mechanism. 12 claims were allowed. The original
model, which was mounted on a flat plate, and later models having
castings, have been preserved. One has a "rule-and-pointer" type character
counter mounted above and to the rear of the keys, where it can be
easily seen by the operator.
The first models perforated at a slight diagonal across
the tape, for use with BLUE CODE and GREEN CODE transmitting units.
Subsequent production units had the perforated holes aligned perpendic-
ular to the center line of the tape, the accepted standard for sensing
stationary tape. Western Union preferred an "advanced" feed hole,
the left edge of which was in line with the left edge of the larger
"code" holes. Other customers, including the Bell System, specified
or accepted the Morkrum "in-line" feed hole, the center line of which
was the same as that of the "code" holes. This was a slightly easier
pattern to design, manufacture and inspect.
* REFERENCES: The Patents listed are in Teletype Patent
Organization archives, as follows:
DATE.FILED...PATENT.NO....DATE.ISS.....PATENTEE(S)..........MODEL....CLAIMS
---------------------------------------------------------------------------
...2-03-02.....754,689.....3-15-04...F.Pearne/C.Krum........Relay.Des....13
...1-10-03.....843,283.....2-05-07...C.Krum.................Ringer........6
...8-22-03.....888,335.....5-19-08...C.Krum.................Ptr..Set.....16
...4-11-04.....929,602.....7-27-09...C.Krum.................Keybd........49
...7-11-04.....894,044.....7-21-08...F.Pearne...............Relay.Sel....35
..10-06-04.....862,402.....8-06-07...C.Krum.................Page.Ptr.....32
...8-31-06.....929,603.....8-27-09...C.Krum.................Keybd..Tr....58
...9-06-06...1,004,038.....9-26-11...C.Krum.................Relay.Ckt....30
...1-22-08...1,199,011.....9-19-16...C.Krum/H.Krum..........Relay.Ckt....55
...6-01-08...1,172,294.....2-22-16...C.Krum.................Polar.Rel....30
...6-01-08...1,220,433.....3-27-17...C.Krum/H.Krum..........Relay........10
...2-04-09...1,137,146.....4-27-15...C.Krum.................Oliver.Typ...31
..11-29-09...1,232,045.....7-03-17...C.Krum/H.Krum..........BLUE.Code.P..35
..11-29-09...1,305,225.....5-27-19...C.Krum/H.Krum..........BLUE.Code.P...8
...5-31-10...1,286,351....12-03-18...H.Krum.................ST/SP.Sel....38
...6-18-12...1,174,427.....3-07-16...C.Krum/H.Krum..........Keybd..Perf..15
...6-18-12...1,326,456....12-30-19...C.Krum/H.Krum..........Tape.Trans...21
...3-07-14...1,360,231....11-23-20...C.Krum/H.Krum..........S/R.Dstrs....55
...9-08-14...1,182,179.....5-09-16...C.Krum/H.Krum..........GPE.Perf.....12
...5-17-15...1,366,812.....1-25-21...C.Krum/H.Krum..........Tape.Trans...51
...6-30-16...1,434,290....10-31-22...H.Krum.................K/T.Trans....27
...6-30-16...1,635,130.....7-05-27...H.Krum.................Kbd..Trans...21
...6-30-16...1,635,131.....7-05-27...H.Krum.................Kbd..Trans...13
...9-18-16...1,374,152.....4-05-21...C.Krum/H.Krum..........Kbd..Trans...15
..10-13-19...1,738,777....12-10-29...C.Krum/H.Krum..........GREEN.Code...50
..12-23-19...1,635,129.....7-05-27...C.Krum/H.Krum..........M11.Kdb..T...37
..12-23-19...1,635,486.....7-12-27...C.Krum/H.Krum..........M11.TD/SMS...79
..12-23-19...1,676,448.....7-10-28...C.Krum/H.Krum..........M11.Select....6
...1-21-21...1,419,677.....6-13-22...C.Krum/H.Krum..........Tape.Trans...10
...6-13-21...1,570,633.....6-26-26...H.Krum.................M11.Select...14
...6-18-21...1,791,740.....2-10-31...S.Morton/H.Krum........M12.Select...54
..12-28-21...1,485,212.....2-26-24...J.Brady................M11.-.Radio...8
..12-28-21.....Reissue....11-23-26...J.Brady................M11.-.Radio..13
...8-23-22...1,764,316.....6-17-30...H.Krum/J..Carr.........Mux..Fork....51
...8-14-23...1,523,377.....1-13-25...J.Brady................M11.-.Radio..11
...8-22-23...1,562,820....11-24-25...J.Brady................M11.-.Radio...3
..11-07-23...1,665,594.....4-10-28...H.Krum.................M12.Printer..15
..12-23-24...1,745,633.....2-04-30...S.Morton/H.Krum........M14.Printer..52
...7-16-26...1,783,382....12-02-30...H.Krum.................M14.Select...22
...6-19-26...1,769,834.....7-01-30...W.Harding..............GPE.EOL.Ind..28
...4-09-27...1,796,378.....3-17-31...H.Krum.................M14.6-level..19
Document Notes
Note by Jim Haynes: Above document received from Bill Lill 8 Nov 1999. Ran Slayton started
at Teletype about 1946, after working for Western Union. He died in 1998.
This document was formatted by
Gil Smith, July 2001.
The original file,
slayton--tty-patents.txt, is courtesy of Jim Haynes.
Pardon all the periods in the patent table -- I needed to space it out, and pasting together a
proper html table seemed like too much work today.