| 摘要 |
A wireless transmitter and receiver pair is connected to the keypad and the base terminal for transmitting and receiving data over a wireless medium and for detecting an alignment signal, which represents alignment between the keypad and the terminal. An indicator circuit provides a message indicative of a state of misalignment to a user of the keypad in response to a failure to detect the alignment signal. A separate wireless position detection system determines the keypads position with respect to the base terminal's zone of transmission, and displays a message to the user for adjusting the position, if necessary. In Point-Of-Sale transaction terminals, the keypad can be used to enter data, while affording the user the comfort and security of being able to hold the keypad close to his or her body.
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