SUBCOURSE 410, LOCAL-BATTERY TELEPHONE PRINCIPLES
12 CREDIT HOURS
The study of telephony includes a study of sound and the principles used to convert sound waves into
electrical implies. These impulses are transmitted over wires or other media and reconverted into sound waves
similar in form to the original waves. This feat was first accomplished by Alexander Graham Bell in 1876. Since
that time, the telephone has become one of our primary means of communication.
The principles used by Bell when he invented the first telephone are still practical and are used extensively in
military applications. In stable or semifixed situations, the more expensive and complex automatic dial telephone
system is used. However, the simplicity of design, the sturdy construction, the ease of operation, the reduction of
maintenance, and the low initial cost make the local-battery telephone system particularly suitable for tactical
The local-battery telephone system is desirable because of the rugged construction of its components and their
ability to provide dependable communications over long distances and under adverse conditions.
The purpose of this subcourse is to teach you the fundamentals of telephony and prepare you for continued
study on the more complex, more advanced elements of telephone communications.
This subcourse consists of five lessons and an examination, as follows:
Lesson 1. Sound and Telephony
Lesson 2. Local-battery Telephones
Lesson 3. Operation of Local-Battery Telephones
Lesson 4. Operation of Sound-Powered Telephones
Lesson 5. Operation of Amplifier Telephones
Credit Hours: 12
You are urged to finish this subcourse without delay; however, there is no specific limitation on the time you
may spend on any lesson or the examination.
Texts and materials furnished:
TM 11-678, Fundamentals of Telephony, March 1953 (EXTRACTED)
REVIEWED AND REPRINTED WITH MINOR REVISIONS JULY 1976.