(4) By the use of on-line security devices, messages can be automatically encoded and decoded during
transmission and reception. This makes a teletypewriter circuit more secure than any other method of
(5) Precedence for message handling can be established. Messages can be arranged so that those of
greater urgency can be sent with shorter delay time than those of lesser urgency.
(6) Automatic operation minimizes human error and individual characteristics in message transmission.
If transmission is by automatic means, messages are placed on perforated tape. If procedure is
correctly followed in message preparation, the "personal" touch given to electrical communication is
minimized. Thus, there is less chance that the message transmission will disclose unit identification
and tactical deployment.
(7) Voice frequency (VP) telegraph uses narrowband transmission. A large number of channels can be
placed in the same spectrum occupied by a voice channel by using multichannel terminal equipment.
(8) Telegraph transmission, either dc or VF, minimizes the effect of noise. Until noise exceeds the pulse
amplitude needed for character identification, it will have no effect.
(9) Telegraph distortion (shortening or lengthening of signal pulses) is not evident until it reaches the
magnitude that results in misprinting. In other words, signal distortion is not noticeable in the
message unless the distortion becomes so bad as to cause misprinting.
i. Disadvantages of Telegraph Transmission.
(1) Skilled people are needed to prepare the messages for transmission. Skilled people are also required
for the process of message transmission and reception over the complete circuit.
(2) Teletypewriter messages lack the personal touch that telephone communication allows.
Teletypewriter messages are cold, matter-of-fact communications.
(3) A relatively large equipment investment and inventory are required to achieve teletypewriter
communication. This is especially true if multiple-channel operation is specified.
(4) A teletypewriter communication system is a complex arrangement, both as to system characteristics
and equipment requirements. The complexity and multiplicity of equipment, especially in larger
units, demand the use of an adequate maintenance organization.