A vertical shaft motor drives a toothed wheel which strikes an anvil fastened to the center of the sounding diaphragm

To make the picture complete, let us imagine that after a time you hear a single-stroke gong sounding number four, three (4-3). This may designate a fire in the pattern shop, or may simply be an agreed call for a fire-drill.

For contrast, let us go to an out-of-date, shabby, primitive foundry, which is still running on the "chance and luck" principle, found to be satisfactory by our forefathers. In those days a molder received a dollar or two for a 12-hour day, and the output was measured in pounds where it is now stated in hundreds of tons. Two or three office boys are running all over the works trying in vain to locate the superintendent who is needed in the office to help on a very important quotation. When he is finally located, it is too late to take care of this matter in the proper way. A millwright is needed in a hurry to take care of a hot bearing on a rush job, and nobody knows where he is. He happens to be attending to an unimportant job in a dark pit, and is blissfully ignorant of the fact that he is urgently needed elsewhere.

Actual experience not only in foundries but in all kinds of industrial establishments has demonstrated the importance of audible signals in promoting both the efficiency and the safety of operations. Horns, bells and whistles are simple pieces of apparatus available on the market. Their cost is trifling in comparison with their useful service, and any far-sighted foundry manager can readily see the great advantage of equipping his works with acoustic signals, once the matter has been properly brought to his attention.

A Code-Calling Device

Fig. 2 shows a simple device for sounding simultaneously any desired number of horns, whistles and gongs scattered throughout the works, and for calling various persons according to a prearranged code. The electrical connections are shown in Fig. 3. The device consists essentially of a number of toothed wheels which close and open an electric circuit in a certain sequence. These wheels are mounted on a shaft operated by a clock spring. A drum is provided with a combination of 40 simple arrangements of contacts, such as 1-2, 1-3, 2-3, 1-1-2, etc. The horns are connected to an

The operator sets a code number and pulls on a handle. This closes the electric circuit the required number of times, and makes the horns and the belis sound throughout

the plant

available 110 or 220-volt circuit, either direct or alternating current, while only a small current from a few dry cells is used in the central instrument. This current closes a relay which operates the power circuit between two contacts especially designed for frequent opening.

When it is desired to call some person, the code handle A is set on the number assigned to that person, and the

operating handle B is turned by one-half a revolution. This is all the operator has to do. The contact shaft is set in motion by the spring and the circuit is closed a certain number of times in accordance with the position of the code drum. Every time the battery circuit is closed the relay closes the power circuit and operates all the horns, whistles, gongs or lamps connected to it. Having sounded the complete call three times the handle B returns to its original position and the mechanism is ready for the next call.

In most cases it is considered sufficient to sound the call number three times. The first time the person may not be sure whose call it is, the second time he counts the sounds and the third time he checks himself. For exceptional purposes, the call may be sounded more or less than three times or even continuously until stopped.

The operation of the code-calling mechanism is usually entrusted to the telephone operator, where a private branch exchange is available. If the manager needs Mr. Jones and fails to reach him by telephone at his desk, he tells the telephone operator to sound his call number. Mr. Jones may

be anywhere in the works, but as soon as he hears his number he comes to the nearest telephone and reports to the telephone operator who immediately connects him with the manager's telephone. Special cases have arisen in which the operation of the code-calling instrument had to be entrusted to a clerk in the superintendent's or production manager's office, in order to prevent office boys, clerks, etc., from disturbing important members of the staff on trifling occasions. The operator of the calling device is supposed to inquire about the nature of the business before starting the call.

When the number of persons to be called is not great, say 10 or 12, it is sometimes convenient to assign two or three different numbers to the same person. These three numbers may mean respectively: (1) "Call me on the phone immediately;" (2) "Call me when through with the present engagement;" (3) "Come to the manager's office."

The particular rules for the use of the code-calling equipment differ from factory to factory in accordance with

the local conditions, and may be modified from time to time as actual experience indicates.

Some care must be exercised in the selection of the type of sound-producing signals and of the number of such devices in each department. A buzzer or a bell would not be heard near a tumbling barrel or a sand disintegrator; on the other hand, a powerful electric horn would be out of place in an office.. Each signal must be distinctly heard under the most intense noise possible in that department by a person most unfavorably situated with respect to the signal. At the same time it would be a mistake to use unnecessarily strong signals, which are liable to get on the workers' nerves.

The pitch of the signal (high or low voice) is another factor to be considered, and while no accurate experiments

FIG. 3 THE ELECTRICAL CONNECTIONS FOR THE CALLING MECHANISM

A local battery closes a relay, which in turn closes the power circuit to which the audible devices are connected in parallel

are available, the selection should be governed by the principle of contrast. In a shop with a low-pitch rumbling and howling noise a shrill signal is more liable to be heard, and vice versa. Again, where the noise is of a discontinuous percussion type, like hammering or riveting, a horn with its steady sound would immediately attract attention. On the other hand, where the noise is continuous like that of a blower, a loud single-stroke bell might cut through the noise more readily.

Acoustic signals are so inexpensive that it is an easy matter to change them, or to change their position and number, should the first installation be not quite satisfactory