The devices use the existing home tape recorders, call recording can be both, at home, no one can automatically answer and record each other's message.
Circuit as shown by the ringing detection, audio detection, RS flip-flop, answer voice modules and analog electronic switches and other components. When the owner out when S1 is set to "1" bit, the circuit in the automatic message state. If you call the machine, telephone lines X1, X2 ringing signal sent (90V, 25Hz) by the blocking capacitor C1, the current limiting resistor R1, by the VD1 ~ VD4 rectified output DC voltage is applied to the optocoupler ( 4N25) feet, feet conduction between the optical tube. So pin output level jump from 0 to 1, add to the IC3 (TP-1106K) feet, triggering its work.
IC1 2 S 1 using three analog electronic switch CD4053. RS flip-flop IC4 form by the NOR gate CD4001. R3, C2 for the automatic reset circuit, the instantaneous power, because the voltage across C2 can not be mutated, S-side controlled by IC5 1 foot, so the RS = 11, output Q = 0; then C2 is charged, R-side down is low, that is, RS = 01, then Q = 0 state will be maintained. S2 is the set switch. Use of the audio detection circuit IC5 NJM2072, the interior includes audio amplification, detection, analog electronic switch, Schmitt trigger, buffer amplifier and constant current source, etc., output pins are complementary, no audio signal input pin, pin 1, feet 0; a signal foot change 0, foot change 1. Cancel the audio signal, pin output hold time from the C7 decision of the general estimate can be T = 0.2C7. RP used to adjust the amplification gain, change detection sensitivity. To sum up, after power-on control side were initialized to: IC5 of pin 1, feet to 0; RS flip-flop of Q = 0; IC1 control of the three electronic switches are side A1 ~ A3 0, ie {12}, {14} feet conduction, foot turn, {15}, the foot turn.
As mentioned above, if ringing signal is high when the pin is triggered IC3 audio signal is output by IC1 {12}, {14} feet, and C5 is increased to IC5 feet. Changes at this time IC5 feet, RS flip-flop input RS = 00, Q = 0 the output state is still maintained; and IC5 feet to 1, on the one hand added to the electronic switch feet, to{15 } feet and respectively, on-foot, IC3 foot issued a "Hello! owner is away, please be brief message," the voice message by IC1 {12}, {14}, {15} feet, and C3, S1 transfer to each other, waiting for a message; the other hand the positive side emitting LED, triac BCR turn, connected to the recorder power supply, the motor starts to rotate (previously installed tape, and press the record button and power switch). But this time IC3 {13}, {14} leg is broken, so the tape is just idling, rather than the output pin will IC3 response signal recorded to tape. MIC jack on the recorder which then P3, P4 power connector for the tape recorder, P5 AC power connection.
When the IC3 acknowledge output pin after the end of an identity of its positive pulse output pin, and added to the S side to flip the trigger, the Q output from 0 to 1. At this time, electronic switch IC1's Jie AUTHOR Ze feet to 1 {14}, {13} feet turn, leave a message through the C3, C4, and IC1 on-foot {15}, {14}, {13 } and feet by P3 into the tape recorder and record to tape. During the response and the message, IC5 always have the audio signal input pin. When the message after the end, IC5 foot out the audio signal, pin output variable 0, IC1 feet to 0, IC1's {15}, feet and feet off. At the same time become an IC5 of feet, triggering RS flip-flop flip, so that Q = 0, IC1 {11} feet to 0, {14}, {12} feet reconnected, the circuit returned to the initial waiting state, waiting the next message. Because smaller C1, R1 is high, the other message will not make optocoupler turn signal work.
When S1 is set to "2" bit is connected to telephone TEL, to normal closing bell and make a call, then IC2, IC3 no effect. Call IC5 feet audio signal, so its output pin 0, RS flip-flop Q = 0 (see above), IC1 {14}, {12} feet in the conduction state; and IC5's foot change 1, IC1 The {15}, feet and feet on (this time it kicks useless.) Then if you want to call recording, press the tape recorder so that BCR turn the power switch (for IC5 has 1 foot), and press the record button, then press of the S2 triggered RS flip-flop, so Q = 0, then IC1's {14}, {13} feet turned and began to telephone recording, recording finished IC5 feet to 0, the recorder from the stop.