| 摘要 |
<p>A standard keyboard or keypad (14) for a coin operated telephone (2) is connected to balance an artificial line (43) rather than the actual phone line. The artificial line (43) simulates operating conditions at the end of the loop regardless of whether the phone that the keyboard is in is actually near or far from the central office (4). As a result, the standard keyboard (14) can be operated using a current at or near its designed minimum operating current. Additionally, a microcontroller (110) for controlling the operation and decoding of the keyboard (14) is programmed to have a small duty cycle of on time during decoding so that the bulk of the power normally used by the microcontroller (110) can be switched to the keyboard (14) when it is detected that a key is depressed. Thus, a line powered low power controller (3) can be used in conjunction with a standard keyboard (14). By reducing the number of lines used to connect the standard keyboard (14) to the controller, an extra line is made available which allows the controller to be utilized with either a standard or a modified keyboarrd (14').</p> |
