| 摘要 |
Single-channel-per-carrier communication systems (SCPC) it is frequently desirable to add an auxiliary signal, such as low frequency teletypewriter signals (TTY) to a primary signal being transmitted, such as a voice signal, without interference between the auxiliary and primary signals. To accomplish this addition without interference, means (18) are provided for combining the auxiliary signal with the primary signal only after the primary signal has already been processed for transmission. The auxiliary signal has a frequency different than that of the first signal so that a composite frequency division muliplexed signal (FDM) is formed containing said processed primary signal and the unprocessed auxiliary signal. The composite FDM signal is then modulated with a common carrier and transmitted over a common communication channel. |
