Electrical Communication is a free textbook on the basics of communication technology. See the editorial for more information.... |
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Type D Carrier Telephone SystemThe type D carrier36 provides one talking channel and is sufficiently low in first cost and maintenance to be economical for installation on open-wire lines about 100 miles in length. It is a carrier-suppression system, transmitting one sideband. The frequencies used are indicated in Fig. 18. This system employs a self-oscillating modulator and demodulator, thus combining modulation and demodulation with carrier generation. The DA system contains an amplifier for increasing talking distances to about 200 miles.
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