SUMMARY

Now that you have completed this chapter, a short review of what you have learned is in order. The following summary will refresh your memory of basic systems equipment, its principles, terms, and typical circuitry required for you to understand this concept.

A RADIO SET CONTROL UNIT is used to remotely control certain transmitter and receiver functions.

TRANSMITTER TRANSFER SWITCHBOARDS selectively transfer remote control station functions and signals to transmitters.

RECEIVER TRANSFER SWITCHBOARDS transfer receiver audio outputs to remote control station audio circuits.

A TRANSMITTER generates an rf carrier, modulates it with intelligence, amplifies it, and applies it to an antenna.

An ANTENNA COUPLER is a device used for impedance matching between an antenna and a transmitter or receiver.

A RECEIVER receives electromagnetic energy (rf) and may convert it to a visible or audible form.

MULTICOUPLERS patch several receivers or transmitters to one antenna. They also filter out harmonics and spurious responses, and provide impedance matching.

MARKING is when a circuit is closed and current flows in teletypewriter operation.

SPACING is when a circuit is open and no current flows in teletypewriter operation.

INTELLIGENCE is any signal that conveys information (voice, teletypewriter, facsimile).

A START unit is the first unit of a teletypewriter signal. It is always a space.

A STOP unit is the last unit of a teletypewriter signal. It is always a mark.

A TRANSITION is the time it takes to shift from a mark to a space condition or from a space to a mark condition.

A CODE in teletypewriter operation is a combination of mark and space conditions representing symbols, figures, or letters.

NONSYNCHRONOUS teletypewriter operation is when both transmitter and receiver do not operate continuously.

SYNCHRONOUS teletypewriter operation is when both transmitter and receiver operate continuously.

WORDS-PER-MINUTE is an approximate rate of speed. It means the number of five letter words with a space between them that can be transmitted or received in a one-minute period.

BAUD is a measurement of speed based on the number of code elements or units per second.

BITS-PER-SECOND is an acronym of the words binary digit. One bit is equal to one signal unit or element.

NEUTRAL teletypewriter operation is where current flow represents a mark and no flow represents a space.

POLAR teletypewriter operation is where current flow of one polarity represents a mark and current of the opposite polarity is a space.

RUNNING OPEN is the teletypewriter condition where the type hammer constantly strikes the type box but does not print or move across the page.

A KEYER is a device that changes dc pulses to mark and space modulation for teletypewriter transmissions.

A CONVERTER changes an audio signal back to dc pulses during teletypewriter reception.

AUDIO FREQUENCY TONE SHIFT systems use amplitude modulation to change dc mark and space impulses into audio impulses.

RADIO FREQUENCY CARRIER SHIFT systems use a keyer to shift a radio frequency signal above or below an assigned frequency. These shifts correspond to marks and spaces.

A TELETYPEWRITER is a machine that can transmit and or receive letters, numbers, or symbols. It may have a keyboard similar to a typewriter.

A PERFORATOR is a device that stores a teletypewriter message on a paper tape by punching Baudot coded messages into it.

TRANSMITTER DISTRIBUTOR is a device that reads Baudot code from paper tape and allows a message to be sent or a message to be printed on a page printer.

A REPERFORATOR stores an incoming tty signal on paper tape.

A PAGE PRINTER prints teletypewriter characters one at a time in a full-page format. This is usually a high-speed printer.

RED is the reference color of equipment that passes classified information. It normally refers to patch panels.

BLACK is the reference color of equipment that passes unclassified information. It normally refers to patch panels.

A PATCH PANEL is used to tie a receiver or transmitter to its associated equipment.

A COMPARATOR compares incoming signals and selects the strongest to be fed to a teletypewriter through a patch panel. This is used in diversity operation

A LISSAJOUS PATTERN is a combined, simultaneous display of the amplitude and phase relationships of two input signals on a crt.

A TONE-TERMINAL set converts tty dc pulses into audio tones for modulation of a transmitter in audio-frequency tone shift transmissions.

MULTIPLEXING is the process of transmitting a number of intelligence signals simultaneously over a single rf carrier.

TIME-DIVISION multiplexing is the process that periodically samples several intelligence signals. This can be a received signal or one to be transmitted.

FREQUENCY-DIVISION multiplexing transmits and receives the full 360 degrees of each sine wave.

FACSIMILE is the method for transmitting and receiving still images. These images can be maps, photographs, and handwritten or printed text.

SCANNING is the process of subdividing a picture in an orderly manner into segments. This is used in facsimile transmission.

FRAMING is the process of synchronizing a facsimile receiver to a transmitter. This allows proper picture reproduction.

TEMPEST is a term normally used to describe compromising emanations. These emanations are unintentionally radiated signals that could disclose classified information.

ELECTROMAGNETIC INTERFERENCE is a term used to describe the degradation of a receiver or system by externally produced rf energy.