Tone circuit for a the paging receiver for generating pulses of a constant pulse frequency with a variable probe ratio and modulated with a unique alarm sound signal

摘要

PURPOSE:To simplify the circuit configuration of an escalating alert mechanism by changing the I/O duty factor of an alert signal in an alert signal generating part which generates an alert tone gradually according to the lapse of time. CONSTITUTION:A counter circuit 23 outputs a reset signal at every count of a clock signal by eight seconds. An encoder circuit 24 sets the I/O duty factor of the alert signal at 1:7 for eight seconds after the start of ringing. The I/O duty factor of the alert signal is set at 1:3 for the following eight seconds, and that of the alert signal is set at 1:1 for the next eight seconds following that. As a result, the sound pressure of the alert tone is increased gradually at every eight seconds. Therefore, it is possible to obtain a satisfactory escalating alert function without generating the change of tone color by changing the I/O duty factor due to the fact that the frequency characteristic of a speaker 7 is a narrow-band and a coefficient applied to a higher harmonic component.