89C51製作家庭保全系統，可由鍵盤設定啟動或關閉監控，也可由戶外撥入電話來啟動或關閉系統，當有異常時，會播出預設的電話號碼，並播放語音留言-89C51 production of home security systems, can enable or disable the keyboard settings to enable or disable monitoring, incoming call may also be outdoor system, when abnormal, will broadcast the default phone number, and play back voice messages