Rfcs Send System

Figure 3-23 shows an rfcs teletypewriter transmit communications system. You should refer to this figure frequently while reading the functional descriptions of the equipment shown.

Figure 3-23. - Rfcs transmit (send) system.

TELETYPEWRITER SETS. - Most of the teletypewriter sets used by the Navy belong to one family of tty equipment. This equipment features various weights and sizes, quiet operation, and high operating speeds. They present relatively few maintenance problems. Because of this they are well suited for severe shipboard conditions of roll, vibration, and shock.

These teletypewriters operate at various speeds. Conversion from one speed to another is usually only a matter of changing the gears that are located within the equipment.

Teletypewriters may be send/receive units or receive only units. They may be designed as floor models, table models, or rack and wall-mounted sets. The teletypewriter shown is a send/receive floor model.

The teletypewriter receives messages and prints them on page-size copy paper. In addition, it can receive and record messages on perforated tape. You can use the keyboard or perforated tape to send messages. Page print monitoring is available with both methods. The set shown can prepare perforated and printed tape for separate transmission. It does this with or without simultaneous transmission and page-print monitoring. The combinations of services available are extensive.

The tty set may include a CABINET, KEYBOARD, PAGE PRINTER, TYPING PERFORATOR, TRANSMITTER DISTRIBUTOR, TYPING REPERFORATOR, power distribution panels, and a power supply.

In operation, the components are linked by electrical or mechanical connections. You are given a wide range of possibilities for sending, receiving, or storing tty messages. All equipment components are housed within the cabinet. Transmission signals are initiated through the keyboard (kybd) or through the transmitter distributor (td). Signals received or local transmissions can be monitored on the page printer. The typing perforator and typing reperforator are devices for preparing tapes on which locally initiated or incoming tty messages can be stored for future transmission through the td.

COMMUNICATION PATCHING PANELS. - Ttys are provided flexibility by jacks that are used to terminate all ttys and associated equipment. The jacks are wired in communications patching panels, usually referred to as tty patch panels. You are able to connect any combination of equipment electrically by means of patch cords.

The plugs on the patch cords are inserted into the jacks at the front of the panel. These plugs have three different parts. They are the tip, ring, and sleeve. The tip carries the intelligence signal while the ring carries the synchronizing (step) or timing signals. The sleeve carries an alarm signal that indicates (both visually and audibly) a problem to the operator. The problem may be equipment failure, loss of loop current, or improper patching. Commonly used combinations of equipment are often wired together within the panel (called normal-through). Individual pieces of equipment are wired on jacks to allow you to use them alone or in combination.

Tty patch panels also furnish a central point for connecting the dc voltage supply into the tty circuits. One source of supply can be used for all circuits passing through a particular panel.

RED and BLACK are used on patch panels to identify whether that panel is used for passing secure or nonsecure information. Red indicates that secure (encrypted) information is being passed through the panel. Black indicates that nonsecure (unencrypted) information is being passed. Patch panels through which secure information is passed are indicated by a red sign on the front that has inch high white block letters that say "RED PATCH PANEL." Panels through which nonsecure information is passed are indicated by two black signs on the front with inch high white block letters. One sign says "BLACK PATCH PANEL" and the other "UNCLAS ONLY."

Each panel contains six channels. Each channel has its own series circuit of looping jacks, set jacks, and a rheostat for adjusting line current. The number of looping and set jacks in each channel varies with the panel model. Each panel includes a meter and rotary selector switch for measuring the line current in any channel. There are six miscellaneous jacks. Any tty equipment not regularly assigned to a channel, may be connected to one of these jacks.

If the desired tty equipment is wired in the same looping channel as the radio adapter used, no patching is required. But, if the desired tty is not wired in the same looping channel as the keyer or converter, it must be patched. For example, let's put a tty on channel 1 and a converter on channel 3. If you want to receive, you must insert one end of the patch cord in the set jack for channel 1 and the other end in either one of the two looping jacks of channel 3.

In any switching operation between the plugs and jacks of a tty panel, the cord plug must be pulled from the looping jack before you remove the other plug from the set (machine) jack. Pulling the plug from the set jack first opens the circuits to the channel, causing all tty messages in the channel to be interrupted.

Removing the set (machine) jack before the looping jack exposes a dangerous dc voltage on the exposed plug.

Q.23 Most Navy tty sets operate at what speeds?
Q.24 A receive tty set provides outputs in what formats?
Q.25 What does the color red indicate on a tty patch panel?

CRYPTOGRAPHIC EQUIPMENT. - Cryptographic equipment is used to ENCRYPT and DECRYPT tty messages that require security handling. (Encrypting is the method used to code a transmitted message; decrypting is used to decode a received message.) To code or decode any message, the send and receive cryptographic equipment must be compatible.

REMOTE TRANSMITTER CONTROL UNIT. - The remote transmitter-control unit is mounted close to the kybd and permits remote control of the transmitter (xmtr). It has a transmitter power on-off switch, a power-on indicator lamp, a carrier-on indicator lamp, and a three-position rotary selector switch. For rfcs operation you set the switch to CFS SEND to transmit and to CFS REC to receive. Use the TONE S/R position for both transmitting and receiving afts signals.

An audio frequency tone-shift system will be discussed later in this chapter.

TRANSMITTER TRANSFER SWITCHBOARD. - The transmitter transfer switchboard is used in this system to connect the remote transmitter control unit to the radio transmitter.

RADIO TRANSMITTER. - The radio transmitter transmits the tty signal. You should be careful when tuning the transmitter for rfcs operation. The carrier frequency setting is critical and must be properly set to ensure a correct output from the transmitter.

Q.26 What are the functions of cryptographic equipment?