Serial digital signal transmission

Following the source encoder, the resulting serial digital signal is applied to the input of the channel encoder, a device that modulates the transmitted RF wave with the reduced-rate audio information. Auxiliary serial data, such as program information and receiver control functions, also can be input to the channel encoder (or combined within the source encoder) for simultaneous transmission. 

After the analog signal has been converted to digital form the next step is to make the digital data available to the computer. There are two major modes of signal transmission serial transmission and parallel transmission. 

Self-adaptive control, 436-38, 662-67 Self-regulating systems, 7, 34, 180 Self-tuning regulator, 437-38, 662-67 references, 447, 673 Serial transmission, digital signals, 561 Servo problem (see Feedback control)... 

In the serial mode, the digital word (number) is sent to the computer one bit at a time. Now a binary counter provides a parallel output since each of the output bits has its own data output channel and the value of each output bit is simultaneously available. To use a serial transmission scheme, this parallel output must be put into serial form. One way to accomplish this is to use a Universal Asynchronous Receiver Transmitter (UART). The detailed operation of the UART will not be given here as it is not germane to the subject of this book. It is sufficient to say that the heart of the UART is a shift register and the shift register is strobed by a signal from the computer that displaces the binary number, bit by bit, sequentially from the register to the computer. 

RS-232-C In asynchronous transmissions, a recommended standard interface established by the Electrical Industries Association. The standard defines the specific lines, timing, and signal characteristics used between the computer and the peripheral device and uses a 25-pin or 9-pin DB connector. RS-232-C is used for serial communications between a computer and a peripheral such as a printer, modem, digitizing tablet, or mouse. 

The PC must have a serial port - RS232-C or V.24 - which is connected to a modem to transmit data through the public telephone network. Digital bits are converted by the modem to analog signals and reverse. The public telephone net is used up to the next node - PAD of a public data transmission net. There, the data are bundled into packages and addressed. In addition to this there are further possibilities for transmitting data ... 

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