Automatic Telephone Answering Machine

Abstract

An automatic telephone answering machine or system is an electronic device that answers automatically to an incoming telephone call and plays a prerecorded message and is capable of recording a message the caller want to leave. These systems include message recording system having remote acess to message playback, automatic dialing, equipment to receive an alarm, automatic data entry-answering systems and other common telephone devices being used along with modem equipments. The microcontroller typically controls a number of peripherals, components of the answering machine such as an LCD or LED display, an indicator light for recording and playback options, a DTMF receiver and an audio controller. A telephone answering machine must be capble of being remotely activated consisting of:
 A switch deciding the mode of operation either automatic or normal mode.
 Provison for receiving the calls automatically when in automatic mode.
 Provison for recording the message to be deliverd to the incoming user and also to record his mesage
 Storage for the message
 Microcontoller to deliver control signal as per the mode of operation
Commonly used telephone answering devices comprises of a number of features which allow a user to examine the presence of a call, seize calls, play back recorded voice messages, record an announcement etc. Triggering of a telephone answering machine done by counting the incoming ring signals and when the count surpass a preset number set by the user. The machine is programmed in such a way that if the user does not attain his telephone within a specified time period which is the function of number of ring signals, the call is automaticlly answered and a message is palyed back to the caller as well as asks him to leave a message. KEY WORDS: Answering machine, Answering system, Speech compression, ADPCM, Encoding, Decoding