116 Glossary
synchronous: Having a constant time interval between successive bits, characters or events. Synchronous data transmission requires both the sending and receiving devices to use special synchronizing characters to correct variations in timing between the devices. See also asynchronous.
T | Test function: When normal communication is not possible, this | |
function checks the modem, personal computer, and telephone | ||
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| lines to determine if they are normal. | |
| Tone dialing: A dialing method that uses tones instead of pulses to | |
| generate a telephone number. Generally associated with push- | |
| button phones, although some | |
U | connected to pulse lines. | |
upload: To send a file to another computer through a modem. See | ||
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| also download. | |
| UART: Universal Asynchronous Receiver Transmitter is the circuit | |
| interface between the modem and computer. It receives serial bit | |
| data from the modem and converts it into bytes for the computer; | |
| and it converts byte data from the computer into bit data for serial | |
| communication. | |
X | XON/XOFF flow control: A protocol used by devices receiving | |
data. It uses two signals: transfer ON and transfer OFF. The | ||
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| signals are controlled by software. |