| 摘要 |
860,662. Carrier multiplex systems. POSTMASTER GENERAL. Jan. 23, 1959 [Jan. 31, 1958], No. 3329/58. Class 40 (4). In a multi-channel carrier telephone system the carrier frequency of one channel falls within the frequency band of an adjacent channel. As shown, incoming speech signals in the frequency band 300-2200 c/s are passed by high-pass and low-pass filters 1, 2 to a channel modulator 3 where they modulate a carrier of frequency 10.25 kc/s. (A channel) or 9.75 kc/s. (B channel). In the A channel the lower sideband 8.05- 9.95 kc/s. is selected by a band-pass filter 4, and in the B channel the upper sideband 10.05- 11.95 kc/s. is similarly selected. Band-stop filters 5 suppress the 9.75 kc/s. and 10.25 kc/s. carrier leaks. The A and B channels are then combined to form a two-channel sub-group, 8-12 kc/s. approximately, which is translated to any desired position in the frequency spectrum by further modulation and filtration. Limiters 8 prevent overloading of the system by high-level speech signals. |
