Early in the history of the telegraph short lines began to be used for private purposes, and as the Morse code was familiar only to those who had studied it and were expert operators on commercial lines, some system had to be devised that any one with an ordinary English education could use; as the expense of employing two Morse operators would be too great for all ordinary business enterprises. These short lines are called private lines, and the instruments used upon them were called private-line telegraph-instruments. Of course they are now nearly all superseded by the telephone, but they are a part of history.

One of the earliest forms of short-line instruments was called the dial-telegraph. One of the first inventors, if not the first, of this form of instrument was Professor Wheatstone of England, who perfected a dial-telegraph-instrument about the year 1839. The receiving-end of this instrument consisted of a lettered dial-face, under which was clockwork mechanism and an escape-wheel controlled by an electromagnet. Each time the circuit was opened or closed the wheel would move forward one step, and each step represented one of the letters of the alphabet, so that the wheel, like the type-wheel of a printing telegraph, had fourteen teeth, each tooth representing two steps. As the reciprocating movement of the escapement had a pallet or check-piece on each side of the wheel, its movement was arrested twenty-eight times in each revolution. These twenty-eight steps correspond to the twenty-six letters of the alphabet, a dot and a space. On the shaft of the escape-wheel is fastened a hand or pointer, which revolves over a dial-face having the twenty-six letters of the alphabet, also a dot and space. The pointer was so adjusted that when the escape-wheel was arrested by one of the pallets it would stop over a letter, showing thus, letter by letter, the message which the sender was spelling out.

The transmitter consisted of a crank with a knob and a pointer on it, which was mounted over a dial that was lettered in the same way as the face of the receiving-instrument. A revolution of this crank would break and close the circuit twenty-eight times; that is to say, there were fourteen breaks and fourteen closes of the circuit. If now the transmitting-pointer and the receiving-pointer are unified so that they both start from the same point on the dial, and the transmitting-crank is rotated from left to right, the receiving-pointer will follow it up to the limit of its speed. In transmitting a message the sender would turn his crank, or pointer, to the first letter of the word he wished to transmit, making a short pause, and then move on to the next letter, and so on to the end of the message, making a short pause on each letter. The end of a word was indicated by turning the pointer to the space-mark on the dial. The receiving-operator would read by the pauses of the needle on the various letters. This was a system of reading by sight.

There have been many forms of this dial-telegraph worked out by different inventors at different times, and quite a number of them were used in the old days. It was a slow process of telegraphing, but it was suited to the age in which it flourished. One of the difficulties of a dial-telegraph consisted in the readiness with which the transmitter and receiver would get out of unison with each other; and when this happened of course a message is unintelligible, and you have to stop and unify again.

About 1869 the writer invented a dial-telegraph to obviate this difficulty. In this system a transmitter and receiver were combined in one instrument, and instead of a crank there were buttons arranged around the dial in a circle, one opposite each letter. When not in operation the pointers of both instruments at both stations stood at zero. In the act of transmitting the operator would depress the button opposite the letter he wished to indicate, when immediately the pointers of both instruments would start up and move automatically, step by step, until the pointer came in contact with the stem of the depressed button, when it would be arrested, and at the same time cut out the automatic transmitting-mechanism and cause both needles to remain stationary during the time the button was depressed. Upon releasing the button the pointers both fall back to zero at one leap.

The first private line equipped by this instrument was for Rockefeller, Andrews & Flagler, which was the firm name of the parties who afterward organized the Standard Oil Company. This line was built between their office on the public square in Cleveland and their works over on the Cuyahoga flats.

It seemed, however, to be the fate of the writer to make new inventions that would supersede the old ones before they were fairly brought into use. Very soon after the dial-telegraph began to be used, printing telegraph instruments for private-line purposes superseded them. About 1867 a printing instrument was devised for stock reporting, which in one of its forms is still in use. Soon after the invention of this form of printer a company was organized to operate not only these stock-reporting lines, but short lines for all sorts of private purposes. Following the invention of the stock-reporting instrument there were several adaptations made of the printing telegraph for private-line purposes. Among others the writer invented one known as "Gray's automatic printer," a cut and a description of which may be found on page 684 in "Electricity and Electric Telegraph," by George B. Prescott, published in 1877. This instrument was adopted by the Gold and Stock Telegraph Company as their standard private-line printer. It was first introduced in the year 1871, and at the time the telephone began to be used there were large numbers of these printers in operation in all of the leading cities and towns in the United States. While this has been superseded to a large extent by the telephone, there are still a few isolated cases where it is used.

Short lines have multiplied for all sorts of purposes, until to-day the money invested in them largely exceeds the amount invested in the regular commercial telegraphic enterprises.

The invention of the telephone created such a demand for short-line service that some scheme had to be devised not only to make room for the necessary wires, but to so cheapen the instruments as to bring them within reach of the ability of the ordinary man of business.

This problem has been solved (but not without many difficulties) by the inauguration of what is known as the "central station." By this system one party simply controls a single wire from his office or residence to the central station; here he can have his line connected with any other wire running into this same station, by calling the central operator and asking for the required number. It is useless to tell the public that very often this number is "busy," and here is the great drawback to the central-station system. This is especially true in large cities, where there are a great number of lines. The switchboards in large cities are necessarily very complicated affairs, and it requires a number of operators to answer the many calls that are constantly coming in. Each central-station operator presides over a certain section of the board, and as this section has to be related in a certain way to every other section, it is easy to see wherein arises the complication.

In large cities the central stations themselves have to be divided and located in different districts, being connected by a system of trunk lines.