By agreement with Donald Murray, and with his cooperation, the so-called Western Union Multiplex was developed, using Murray’s phonic wheel drive and synchronous correction. Western Union engineers designed tape transmitters and an autocontrol device for transmitting service signals. A keyboard-operated, five-unit-code, tape punch was supplied by the Morkrum Company. A page printer, which was later converted to print on gummed tape, was supplied by the Kleinschmidt Electric Company. The Western Union Multiplex was effective in increasing operating efficiency and came into extensive use throughout the system.
From that time on, development of the Baudot permutation-code printing telegraph apparatus was furthered by various companies, such as Bell Laboratories, Western Electric, the Morkrum Company, the Kleinschmidt Electric Company, as well as the companies of J. E. Wright, L. M. Potts, and others.
It appears that all of these inventors experimented with the idea of operating all transmitting and receiving apparatus at identical speeds to transmit a five-unit-code combination by first transmitting a pulse to start both transmitter and the distant receiver at the same time. Synchronous operation was obtained by electric motors equipped with governors to maintain correct speed; some used tuning-fork-controlled impulse motors. A system of five relays with progressive contact arrangements to cause cascade operation was also used to provide correct timing. Later, when correctly-timed, 60-cycle alternating current became available (see [page 27]), synchronous motors did the job.
Teleprinter apparatus using this synchronous method worked very well for point-to-point transmission as was used by the telegraph companies and news-distributing organizations to carry local traffic. It did not, however, solve the sought-for plan for a teleprinter intercommunicating system. When attempts were made to connect printers at different distant points in a telegraph intercommunicating circuit while using the synchronous principle, false reception and printing errors would occur, due to variation in line circuit conditions and to a variation of the mechanical start operation at outlying teleprinters. This required frequent overline adjustment to keep the connected apparatus in phase.
The following is an excerpt from a patent application of Dr. Louis M. Potts (later to become research engineer for the Morkrum-Kleinschmidt Corporation), filed June 17, 1909, giving his idea for achieving a teleprinter intercommunicating system on the synchronous principle. Dr. Potts was a very capable telegraph engineer. His early association was with the telegraph system of the Rowland Telegraphic Company which had limited use in the early 1900s.
In those synchronous telegraph systems wherein the sending and the receiving commutator brushes constantly rotate, it is necessary to adjust these brushes so that they will approximately simultaneously engage corresponding segments. To effect this adjustment there is usually provided a special device embodying an additional segment on each commutator, and the adjustment consists in causing the brushes to arrive approximately simultaneously on this segment at the two ends of the line. Such adjustment is known as “finding the letter” and has to be made every time synchronism has been interrupted. According to the present invention, the necessity of providing additional means for performing the so-called operation of “finding the letter” is rendered unnecessary, since the transmitting and receiving commutator brushes at the two ends of the line start up afresh as it were for each signal.
In a later patent application, filed October 11, 1913, Dr. Potts stated:
This machine has also the advantage of being able to operate with a very short code. In order to adapt it to Morse circuits, it should be capable of operating with a code at least as short as the Morse code. In the present machine, I preferably employ a five unit code which, together with the starting impulse and the lag between signals, is actually shorter than the Morse code. Counting the five code impulse periods, the starting impulse period and the period of lag between impulses, each signal in my case, may be considered in comparison with the Morse code as being seven units long, whereas the Morse code is 8.5 units long. The average signal being shorter than the Morse, the delicacy of adjustment will be less and the distance of operation greater than a Morse telegraph for the same rate of transmission in words per minute.
Dr. Potts, however, still depended on like synchronous operation at both terminals, and dual start, so he did not have the answer after all!
John E. Wright, who in the 1890s designed and built step-by-step printing apparatus, including the Wright-Negron bulletin printer, also turned his thoughts toward the five-unit permutation code for printer operation and built several variations using the synchronous principle. The Superintendent of Telegraphs for the Delaware, Lackawanna and Western Railroad thought well of Wright’s apparatus and placed some in operation. But, here again, reliable operation could be maintained only in point-to-point operation. As will be noted in [Chapter 2], Mr. Wright’s patents were purchased by the Kleinschmidt Electric Company in 1922.