| 摘要 |
<p>An address coincidence detection circuit (403) detects when a received address matches a stored address (P-ROM 5) and commands an alert pattern generator (405) to provide a corresponding alert pattern (I) with ON durations corresponding to the address in question. Some alert patterns are single-tone, other comprise two alternating tones. A mode controller (404) controlled by the detection circuit (403) selects which kind of alert pattern applies and controls a logic circuit (410-414) which synthesises from a frequency divider chain (406-408) a tone signal (H) consisting of either the single tone or the two alternating tones. This tone signal is gated (415) by the alert pattern (I) to provide the alert signal to an amplifier (6) feeding the pager loudspeaker. The signal tone and one of the two alternating tones has a frequency to which the loudspeaker is resonant.</p> |
