基于单片机的固定电话未接来电告警系统设计OA

To address the lack of missed call alerts in most existing landline phones,which can lead to missed important calls,a sound and light alarm system for landline missed calls based on an AVR microcontroller(ATmega16)is designed and implemented.The system processes the telephone line signal through a preconditioning circuit for voltage reduction and level shifting.The ADC module of single-chip microcomputer samples and analyzes the features of the processed signal,accurately identifying telephone states-idle,ringing,off-hook,and on-hook-using a Finite State Machine(FSM)model.When a ring is detected without a subsequent off-hook action within a set time,the system activates audible and visual alarms via an optocoupler-isolated driver circuit.Test results demonstrate that the system accurately identifies states across various calling scenarios and triggers alarms reliably,effectively alerting users to missed calls and thereby reducing potential risks associated with unanswered calls.