Figure 1: Model AN/UGC-49 Teletypewriter.

One of the more commonly used teletypewriters is the model AN/UGC-49 teletypewriter, shown in figure 1 above. It is an electromechanical apparatus for sending and receiving both printed and tape perforated messages and receives messages electrically from the signal line and prints them on page size copy paper. In addition, it can receive messages and record them on tape in both perforated and printed form. With page-printed monitoring, the teletypewriter electrically transmits messages that are originated either by perforated tape of keyboard operation. It mechanically prepares perforated and printed tape for separate transmission with or without simultaneous electrical transmission and page-printed monitoring. The keyboard, typing reperforator, typing unit, and transmitter distributor are operated by the motor mounted on the keyboard. Selection of these components for either individual or simultaneous operation is by the selector switch located at the front of the cabinet, to the left of the keyboard. All these components are connected in series in the signal line, but the selector switch has provisions for shunting various components from the line. The typing reperforator is operated by a separate motor and power distribution system. It is connected to a separate external signal line.

The keyboard unit (Figure 2 below) provides a foundation for the a.c. motor, typing unit, and typing reperforator. This component incorporates the necessary electrical and mechanical elements for message transmission and for controlling the mechanical printing and perforating of the tape. It also supports the tape container, a character counter used in connection with the typing perforator, intermediate gears for operating the signal generator and typing unit, flexible connections for operating the typing perforator and transmitter distributor, and a three-position selector switch for choosing the mode of operation of the equipment.

The keyboard mounts in the cabinet on rails of a shock-mounted cradle. The front of the keyboard protrudes from the cabinet and is fitted with a rubber seal for a silencing effect. Mechanical power for activating the keyboard is derived from the a.c. motor through intermediate drive gears and the typing unit or the typing perforator, depending on the selected mode of the three-position switch.

Figure 2: AN/UGC-49 Teletypewriter Keyboard Unit.

The typing unit used in the AN/UGC-49 teletypewriter is pictured in figure 3 below. The typing unit incorporates the necessary electrical and mechanical elements to translate the signaling code combinations into mechanical actions that print the messages and perform functions incidental thereto.

Figure 3: AN/UGC-49 Typing Unit (front view).

Paper (single or multi-copy) feeds from a five-inch (maximum) diameter roll mounted at the rear of the typing unit. The paper feeds around a platen which rotates but which does not move horizontally. Type pallets are arranged in a small type box (figure 4 below), which is detached easily for cleaning or replacement. In operation, the type box moves across the paper and presents the proper type pallets to the printing hammer, which drives the pallets and inked ribbon against the paper to print the characters. Combined automatic carriage return and line feed features operate to return the carriage if overprinting occurs at the end of a line.

Figure 4: AN/UGC-49 Type Box (front and back).

As each character is printed, the inked ribbon feeds from one spool to the other reversing automatically when the ribbon reverse lever is tripped by the small rivet at each end of the ribbon. The ribbon mechanism is shown in figure 5 below. Printing is produced by the type box, which contains the characters and symbols shown on the key tops. Operation of keys and space bar moves the type box across the platen from left to right. On each key stroke, the type box is moved into position for the printing hammer to strike the proper type pallet, printing the character on the paper. Operation of the CAR RET key returns the type box to the left margin, and operation of the LINE FEED key moves the paper up to the next line.

Figure 5: Model AN/UGC-49 Ribbon inserted.

Tape preparation, by operation of the keyboard, is accomplished by the typing reperferator (figure 6 below). This reperforator is controlled by mechanical linkages on the keyboard. The reperforator is a transmissable, five-level, chadless, perforated tape with printed characters corresponding to the perforated code. The typing perforator, mounted on the left front corner of the keyboard, is powered through flexible connections and a jack shaft by the a.c. motor mounted on the keyboard. Its tape is supplied from a container mounted at the left rear corner of the keyboard.

 

Figure 6: AN/UGC-49 Typing Reperforator (front view).

With the keyboard selector switch in the K (keyboard) position, the typing perforator is inoperative. (See figure 7 below). In K-T (keyboard-tape) position, the selector switch connects the selector magnet on the keyboard typing reperforator into the signal line circuit of the keyboard signal generator, at the cabinet terminal board, to permit preparation of perforated and typed tape simultaneously with signal line transmission. In T (tape) position, the selector switch mechanically engages linkages between the keyboard and the keyboard typing reperforator resulting in manual typing reperforator operation independent of the signal line.

Figure 7: AN/UGC-49 Selector Switch

The auxiliary typing reperferator is similar in appearance, design and operation with identical sub-assemblies to the typing reperforator already described above. Because the reperforator is not controlled by keyboard but receives messages from an incoming signal line instead, it has a selector unit. The auxiliary typing reperforator is mounted on a special auxiliary base and is powered by an a.c. motor and a separate keyer located in the electrical service assembly. The location of the reperforator in the cabinet is at the top left, above and behind the transmitter distributor.

Both reperforators are provided with a chad chute which discharges the chad from the perforated tape by way of chad chute extensions into a common chad container located under the dome compartment of the cabinet. It is important that the container is emptied frequently to prevent chad from backing up and jamming the perforating mechanism.

The transmitter distributor (figure 8 below) is mounted on its own base in front of the cabinet on the left side. It is a mechanical tape reader used to convert messages on standard five-level chadless or fully perforated tapes to signaling code combinations for transmission on a telegraph channel. The unit includes a start-stop switch in which are incorporated tight-tape, shut-off, and free-wheeling tape feed features. A second switch shuts off the transmitter distributor automatically when tape runs out. Electrical requirements are supplied by way of the terminal blocks in the cabinet through a connector on the transmitter distributor base.

Figure 8: AN/UGC-49 Transmitter Distributor (front view).

Power to the AN/UGC-49 is applied by a switch located on the front of the cabinet, slightly below and to the right of the keyboard. Turning the switch to its upper position, "ON" fully conditions the teletypewriter for on-line service in one of the three modes of operation determined by the selector switch at the left of the keyboard. If the auxiliary typing reperforator is not required, the auxiliary power switch can be turned to the "OFF" position.

To transmit a message directly to the line as it is typed, rotate the selector switch to the K position. The usual procedure in transmitting is to depress the SEND key to unlock the local keyboard. Transmit five spaces, two carriage returns and line feed (in that order) to align the sending machine, and start typing the message. The typing unit monitors the transmission, providing a printed copy of the message. In the keyboard mode of operation, the typing perforator is mechanically isolated from the keyboard, and the character counter mechanism does not function. The transmitter distributor circuits also are inoperable.

Keyboard operation in the keyboard-tape (K-T) mode is the same as when in the keyboard mode, except that typed, perforated tape is simultaneously prepared through electrical connection of the keyboard typing reperforator selector coils to the keyboard signal generator. The character counter is not operative in the (K-T) mode, but the operator can use the monitored page printed copy as a position indicator under those circumstances. The transmitter distributor can be operated.

When the selector switch is in the T position, the keyboard and perforator are isolated from the other units. This mode of operation permits the operator to prepare tape for transmission while transmitting messages via the transmitter distributor, or receiving messages on the printer. The printed character occurs six units after the point at which the five-level code for the character is punched into the tape by the perforator. Since tape preparation is by direct mechanical linkage, typing may be at speeds up to 106 WPM; but a uniform rhythm is required to minimize operator induced error. No page copy is typed in this position, so the character counter automatically illuminates the end-of-line indicator lamp to avoid too many characters for the length of the line. As pointed out previously, the counter registers each spacing character. Non-printing functions, such as FIGS, LTRS, LF, and CAR RET, are not registered.

The transmitter distributor (commonly called the TD) is operable only in the K-T and T modes of operation, and then only when the SEND key is depressed. In the following discussion of the TD, assume that the selector switch is in either the K-T or T position and that the SEND KEY IS DEPRESSED.

To place a tape in the TD, move the start-stop lever to the center (OFF) position. Release the tape lid by pressing the tape lid release button. Place the tape in the tape guide in such a manner that its feed holes engage the feed wheel with the portion of the tape having two perforations toward the read of the TD. Insert printed tape so that the printed, chad side is up. If nontyped chadless tape is used, position the tape so that the open side of the hinged chads is to the top. With fully perforated (chad) nontyped tape, you must be careful to feed the tape from the beginning. Reversing the tape results in garbled transmission. While holding the tape firmly in place on the feed wheel, press down on the tape retaining lid until its latch is caught. Move the start-stop lever to the left (FREEWHEELING) position and manually adjust the tape so that the first character to be transmitted is located over the sensing pins.

Another feature of the TD is the end-of-tape switch. The switch is controlled by a pin protruding through the tape guide plate. As long as this is depressed by tape feeding through the guide, the TD is operable. When the end of the tape passes over the pin, the pin rises and the TD stops transmission automatically. If the tape is torn on the bottom edge, the tape out pin also raises and stops the transmission. For this reason, tapes should be handled very carefully.

((Source: Communications Technician O 3&2 (NAVEDTRA 10235-C), Revised 1975))