| 摘要 |
<p>192,359. Western Electric Co., Ltd., (Assignees of Espenschied, L.). Jan. 25, 1922, [Convention date]. Systems for transmitting music, news, &c.- Amusement is broadcasted from a main distributing station by means of carrier currents superposed on telephone, power or other lines, with amplifying, filtering and rectifying arrangements. Fig. 1 shows the lay-out for such a system with three collecting stations 1, 2, 3 in communication with a main station M which distributes to subscribers through central stations A - - E, amplifiers A1, Aa, &c. being provided at all the stations. Transmission takes place at the collecting stations 1, 2, 3, Fig. 2, at suitable frequencies, and carrier current is supplied either at the collecting station or at the main station from sources S1, S2, S3, with modulators M2, M3, or the transmitter T1 may modulate the carrier current. The incoming carrier currents after amplification are superposed selectively by means of band filters F1, F2, F3 on an outgoing bus 13, which connects to existing lines La, Lb, Lc, Lc to central stations by means of a combination of high-pass and low-pass filters, and directly to subscribers' lines, such as 12. Wireless transmission may also be employed in place of any of these lines. The lines La, &c. are connected inductively at the central stations to a large number of subscribers' lines, condensers being provided to short-circuit the carrier currents with respect to the line jacks. At the substation, the circuit for a loud speaker 26, Fig. 4, is bridged across the line and is tuned by means of a condenser 21 and a variable transformer 22. The selective circuit may be loosely coupled through the transformer to a second tuned circuit containing a condenser 23, across the terminals of which is a detector 25 connected to the loud speaker. An anti-resonant circuit 27 prevents the carrier current reaching the telephone set, or the set may be of the anti-side tone type, the transmitter and receiver being conjugate. Fig. 8 shows the application to an alternating-current power circuit, including a step-down transformer 37, across which are bridged condensers 43, 44 to provide a path for the carrier current. The receiving circuit is bridged across the power circuit, and includes band filters BF1, BF2, BF3 for selecting a desired frequency. The filament and plate currents for a vacuum tube detector 41 may be supplied from the power circuit through a transformer 42 and vacuum tube rectifiers. Carrier current may be used for auxiliary functions such as the switching on and off of motors.</p> |
