| 摘要 |
A telephone line powered system operates in conjunction with a user telephone, and is fully biased off whenever the user telephone is in an "on-hook" condition. When the user telephone is placed in an "off-hook" condition, a hookswitch is operated to cause the system to be supplied with a relatively low level of stand-by power from the telephone line. A micro controller is energized by this stand-by power, and initializes the system. Higher power consuming devices, such as a card reader, a DTMF dialer and the like, remain biased off by the micro controller during the stand-by mode of operation. If information is to be transmitted from the card reader or from an auxiliary program, which is accessed by direct access keys, a switch is closed which causes the micro controller to disable the telephone and to power up the higher power consuming devices. Once operation of the higher power consuming devices is completed, the micro controller causes the system to revert back to its stand-by mode of operation; and control of the telephone line is returned to the user telephone. During the stand-by mode of operation, the power consumption is sufficiently low that the system is essentially transparent to the user telephone.
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