"Kellogg Telephone and Switchboard Exhibit at the
Pan-American Exposition"¹

Fig. 1. Kellogg Telephone and Switchboard Exhibit at the Pan-American Exposition. — Main Booth.

One of the most attractive and conveniently arranged booths at the Pan-American Exposition is that of the Kellogg Switchboard and Supply company of Chicago in the Electricity building. The display made by this company is very elaborate, and its booths, illustrations of which are shown herewith, clearly emphasize this statement. What must still be more gratifying to the Kellogg company is the fact that the excellence of its apparatus has been attested by the jury of awards in assigning to the company a gold medal indicative of the highest award on "telephone systems and apparatus."

In order to exhibit to best advantage the systems and apparatus manufactured by this company it was found necessary to provide two booths. The main booth, illustrated in Fig. 1, is in Section R and contains a general display of its different apparatus, while the company's branch booth in Section F (Fig. 2) is used o display and demonstrate the practical working of subscribers' telephone apparatus.

One of the first things to attract the attention of a visitor upon entering the main booth is a single section of the largest centralized-energy multiple switchboard ever built. The ultimate capacity of the complete switchboard is 12,000 subscribers' lines. A board of this type fully equipped would require about 40 of these sections. It is provided with line lamp signals and double-lamp supervisory signals in the cord circuits. One of the unique features of this board is the simplicity of the spring jacks which are provided with only two terminals and are mounted 40 per strip on three-eighths-inch centers, thus gradually reducing the area occupied by the multiple jacks on the face of the section and making the cabling so simple as to be easily wired and maintained. The cabinet is of a rich, solid mahogany and is provided with a plate-glass panel in the end which enables one to observe the complete arrangement of the multiple cabling. The back of the cabinet is provided with a roller curtain constructed so as to make the board practically dust proof.

At the front of the open space is a plate-glass display showcase which contains an interesting exhibit of small telephone apparatus used in the construction of switchboards and subscribers' outfits. Several important pieces of this apparatus are shown disassembled. A duplicate of this showcase in the rear of the 12,000-line board contains a complete line of samples of fine magnet wire, switchboard and telephone cords, and switchboard cable, all of which form a part of this company's product.

Fig. 2. Branch Booth

Supported on elaborate show boards conveniently arranged in this space is shown a complete line of subscribers' wall sets comprising over 36 different types and finishes. These instruments are all connected to switchboards for demonstrating purposes.

A soundproof booth located in the rear of the space contains magneto and centralized-battery subscribers' sets for testing the quality and strength of transmission and comparison of systems.

Another switchboard shown which is particularly interesting is a two-division centralized-battery lamp-signal switchboard. With this type of switchboard the subscriber is provided with two push buttons which enables him to make, direct connection with either division of a two-division multiple switchboard, thus making it possible to connect directly with the subscriber desired without the use of trunk lines. This arrangement is applicable to cases where it is desired to install a switchboard of a greater capacity than it is possible to obtain with a single multiple switchboard.

A combination centralized-battery and magneto switchboard is also exhibited in this main floor space. This board is intended for use in small towns where it is desired to give the town subscribers the advantage of the latest designs of telephone apparatus and to make it possible to connect magneto lines directly, such as toll lines and long farmers' lines, with the centralized-battery town subscribers. The board has a capacity of 160 centralized-battery lines and 30 magneto lines. All of the central-office apparatus necessary for operating an exchange of this type, except the battery, is conveniently located in the cabinet of the switchboard. Several centralized-battery and magneto instruments are connected to the board to show its operation.

A wall-type switchboard which is also shown has a capacity of 20 magneto lines and is provided with apparatus for four-party-line selective signaling. This particular type of switchboard is largely used for connecting farmers' and toll lines, and its construction is nearly as simple as the regular subscribers' wall set, so that it requires no experience to operate it.

Besides the instruments and apparatus described above, the main exhibition space contains four express-type switchboards ranging from 50 to 200 lines' capacity. These switchboards are provided with mechanically self-restoring drops and a very substantial and convenient arrangement of cord equipment. This type of board represents the simplest forms of telephone exchange equipment for use in small towns where an efficient and rapid means of intercommunication is desired.

At the rear of the main exhibition room just described is an "exchange room" in which is located a centralized-battery "major" switchboard of 3,000 ultimate capacity with a present equipment of 980 lines. All the apparatus necessary to make this a complete working exchange is located either in the room or in the basement under the booth. A large number of subscribers' instruments of different designs located in Sections F and R are connected to this board to show its operation.

Fig. 3. Power Equipment in Basement

The line cables enter the basement through regular underground clay conduit and terminate on the main distributing frame in pot-heads. From these heads a cable made up of rubber-covered wire connects the lines directly with Kellogg protector strips, which are provided with carbon-block lightning arresters and heat rods. These heat rods are used as a protection from sneak currents and are extremely simple in construction and very uniform in operation.

Jumper wire connects the line terminals on the protector side of the main distributing frame to the switchboard side from which cables are led to the relay rack containing both the line and cut-off re-lays. From this rack cables lead to the line side of the intermediate distributing frame and from the switchboard side of this latter frame other cables lead to the answering jacks and lamps on the various sections of the switchboard located in the "exchange room." The multiple cables also lead from this frame and run through the entire length of the switchboard.

Although all of the apparatus shown in connection with this model exchange is necessarily somewhat cramped for lack of space, yet it is so arranged as to be practical in every way.

The arrangement of the switchboard in the "exchange room" is the same as that of an operating exchange. There are three sections of three operators' positions each, the two end positions being left blank. This gives each operator 140 lines each of which terminate in an answering jack with its associated line lamp signal. The key shelf contains a complete equipment of 15 cord circuits for each operator. These cord circuits are provided with ringing and listening keys and double-lamp supervisory signals, there being one lamp signal for each half of the cord circuit.

Each operator's position is provided with pilot lamps which serve as a check or help to the operators.

A rear view of this switchboard brings out a very striking feature in connection with this "model exchange," that is, its simplicity and the small amount of cabling- used in its construction. This is due to the fact that it is operated on what is known as the two-wire multiple system.

The storage batteries for supplying all direct current for the exchange are installed in a room located in the rear of the basement. This room is provided with ample ventilation and a concrete floor sloping to a drain. Each battery consists of 10 Chloride cells, with F-7 elements, 240-ampere-hour capacity, this being sufficient for the present equipment of the exchange. The elements are contained in F-13 tanks, 480 ampere-hour capacity, which are large enough for the ultimate capacity of the exchange. The discharge leads from the battery lead directly to the fuse board located just outside the battery room. From the fuse board wires are led to the individual cord circuits at each section of the main switchboard.

The power switchboard used for handling all heavy currents required in the exchange, such as the currents for the charging and ringing machines, and the charging and discharging circuits of the storage batteries, is located next to the wall of the storage-battery room. It consists of two slate panels mounted on an iron framework and is illustrated in Fig. 3.

Fig. 4. Roof Garden of Main Booth

A duplicate set of charging and ringing machines (shown in Fig. 3) is used in connection with this exchange as an extra precaution against breakdown or the failure of current supplied from an outside source. The machines are of the Holtzer-Cabot type and of the following sizes: The two generators provided for charging the storage batteries from 110 volts direct current are Holtzer-Cabot machines with 1,850 watts output. There are two ringing machines of the Holtzer-Cabot one-fourth-horse-power type; one runs from 110 volts direct and the other from 10 cells of storage battery. These ringing machines deliver 75 volts alternating and pulsating current from their secondary windings.

All the power winding in this model exchange is of the most substantial character and is protected by being drawn into Richmondt steel conduit.

The roof garden (Fig. 4), located over the exchange room of the main exhibit, is reached by a flight of winding stairs similar to those commonly used in telephone exchanges. Suspended over this roof garden from the girders of the building is an elaborate double-faced electric sign nearly 22 feet long and about seven feet high, built by the A. & W. Electric Sign company of Cleveland, Ohio. Each letter of this sign is connected to a flasher located in the basement of the booth, so that the word "Kellogg" can be flashed in various combinations.

In order to demonstrate the operation of the Kellogg systems, and especially the transmission and receiving qualities of the subscribers' instruments, it was found necessary to isolate a part of the exhibit so as to give more nearly the actual condition of the subscriber with relation to the exchange. Thus the branch booth in Section F was designed solely for this purpose. This space (Fig. 2) is provided with two soundproof telephone booths such as are used for long-distance transmission work. These booths are both supplied with centralized-battery and magneto subscribers' instruments which are connected by artificial lines to the switchboards located in the main exhibit.

The architectural design and arrangement of these booths is well balanced, and with the extensive exhibit go to make up one of the largest and most interesting collections of telephone apparatus ever shown to the public.