| 摘要 |
A battery saver circuit for a tone coded personalized radio pager device or the like is described which includes a switchable frequency tone filter to detect a predetermined sequence of tones. One of several alert signals is generated when the correct sequential tone code of the device has been detected. Power is periodically applied to a receiver by a power supply circuit and a control circuit. The first code tone is sampled three times to protect against false identification of this tone. After this first (preamble) tone has been validated, power is supplied for an additional duration of time and the filter is set to detect the next code tone. Once the second code tone has been detected, if the next code tone is not detected within a predetermined time window, the control circuit resets the switchable filter to again search for the second tone of the code. By resetting the filter to detect the second tone, it is possible to condense the broadcast time required for a string of coded messages.
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