Jim:

I thought that you might be interested in seeing this manuscript that I found
at the Chicago Historical Society while researching my thesis. I think it may
have been written by Howard and Charles Krum since their names were penciled on
the front, but I can't verify one way or the other.

Tom Schumacher

Morkrum Company. (1911). The Morkrum Telegraph Printers. Chicago:
Author. [Names of Charles and Howard Krum written on cover.] 11 pp.

The Morkrum Printing Telegraph

The Morkrum Printing Telegraph is a direct acting keyboard system; that is, the operation of the keyboard at the sending end actuates the printing mechanism at the receiving end directly, without any intermediate operations.
Upon the simplicity of the line currents used, depends the
ability of a printer to operate successfully under the varying
conditions of weather and line interference, met with in actual
work; to meet these requirements, the reliability of the Morse
polar duplex has been taken advantage of, and the system almost
exactly duplicated in the Morkrum Printer.
The current is of single strength, with the battery always
connected to the line, and the signals are transmitted by reversals
of polarity. This system gives the advantages of the Morse polar
duplex, in its ability to work successfully over long lines, and
also makes it possible to repeat through direct point repeaters.
The transmitted signal is divided into six time intervals.
The negative pole of the battery is normally connected to the line
between signals, and it is accordingly essential that a signal be
started by connecting the positive pole to the line.
Figure I shows a signal in which current of positive polarity
is sent to the line during all of the six time intervals. The
first interval is designated as (O) in the diagram, and is known as
the starting interval. The selective signalling is accomplished by
combinations of reversals of polarity of the current sent to the
line during the five succeeding time intervals. This allows
thirty-two selections to be made over the line, and by using a
shift of the type wheel, fifty-three letters, figures and
characters are printed.
This system of selective signalling is illustrated by Figure
II, which shows the signals sent over the line for the word "The."
The letter "T" is formed by reversing the polarity of the current
sent to the line during the third and fifth intervals. In letter
"H" the current is reversed during the second, third, fourth and
fifth intervals, while in letter "E" the reversal takes place
during the second and fifth intervals.
As in this system there is never to exceed three and an
average of only two signalling currents sent to the line, for each
letter, it is not necessary to transmit the signals at a high rate
of speed, in order to obtain the necessary speed on the
transmitting keyboard.
Figure III shows the theory of the action of the receiver in
selecting the different signals. The receiving mechanism is
arranged to connect the selective locks to the line relay for anly
[sic] a short portion of the duration of each time interval of the
transmitting signal.
The system is not synchronous in the ordinary sense of the
word, but is roughly isochronous; that is, the receiving mechanism
is adjusted to run approximately the same speed as the transmitting
mechanism, and a governing rheostat is provided to regulate the
speed of the receiving mechanism, so that the relation of the
received intervals to the transmitted intervals can be correctly
adjusted. This is for the purpose of compensating for any
difference in the voltages of the local power at the two ends.
This arrangement allows of considerable distortion of the
signals before the selection is interfered with, as it is only
necessary that the interval of the receiving mechanism lies
somewhere within the limits of the corresponding transmitted
signal.
The mechanism is divided into a number of elements, the
functions of which and their relations to each other are best
explained by reference to Figure IV, in which "T" is a transmitter
bank of relays, "R" is a receiver bank, and "A" an auxiliary bank.
The combinations corresponding to the different signals are
set up in five pole changers, in the keyboard, one for each of the
five selective intervals. The function of the transmitter bank is
to connect these pole changers successively to the main line pole
changer.
As shown by Figure IV, the keyboard and transmitter bank
control the action of the home recorder relay and the pole changer.
The operation of the home recorder is accomplished selectively
in exactly the same manner as that of the printing mechanism at the
far end.
On the relays the contacts correspond to the "marking" and
"spacing" contacts of a Wheatstone relay, and are so designated.
The marking contact point of the home recorder relay operates
a receiver bank, which acts as a distributor and successively
connects the selective lock relays in an auxiliary bank to the
spacing contact of the home recorder relay. The spacing intervals
of the signal operate the corresponding selective locks, while the
marking intervals leave them unoperated. The lock relays in the
auxiliary bank control the mechanism of the printer, the actual
selection of the letter being accomplished in the printer.
The first four intervals control a mechanical selecting
device, which interposes the proper stop pin in the path of the
typewheel arm, and the fifth interval governs the direction of
rotation of the typewheel, and completes the operation of printing
the letter.
In a duplex set the contact points of the main line pole
changer are connected to the two poles of the main line battery,
while the tongue is connected through a ground switch to the split
of the main line relay.
After leaving the main line relay, one side passes through a
differential galvonometer to the main line, while the other side
passes through the galvonometer to the artificial line.
The contact points of the main line relay control the action
of the receiver bank, auxiliary bank and receiving printer, in the
same manner as in the home recorder, previously described.
A three point switch is arranged so that the marking contact
of the main line relay may be connected to a Morse sounder, if
desired.
The receiver and home recorder are identical and
interchangeable; these, and also the transmitter bank and keyboard
are provided with slip connections so that any one of them may be
instantly removed and another element substituted.

Reliability and Workmanship.

Realizing that if identical results were to be obtained,
identical machines must be built, the Company has equipped a
factory with the finest machinery, and has built tools, dies and
special machinery to insure accuracy and interchangeability of
parts, to the careful design and accurate construction of which
much of the success of the printer is due.
After preliminary line trials, operators were put on the
machines, and tested for months before being put into actual
service, and a high degree of reliability was thus developed.

Capacity.

A duplex set installed for the Postal Telegraph Cable Company
between New York and Boston has now been in daily service for
nearly a year, and the machines are showing a capacity for handling
heavy traffic, having handled over one thousand messages in a nine-
hour day. One postal operator made a record of sending 74 messages
in an hour and 66 messages the following hour. Nearly a good a
record was made by an operator of the C. B. & Q. Ry. on a set
installed between Chicago and Galesburg, who sent 71 and 65
messages in two hours.

Printers Installed and Rented.

The Printers are placed on a rental basis, the Company sending
out instructors to install, and instruct operators and attendants.
More defininte information as to terms and contracts will be given
upon application.