Homemade small telephone program-controlled switch circuit diagram

Circuit Principle: When an outside call is made, the ringing pulse charges C2 through C1, R1, and D2, and the voltage is stabilized at 6V. This voltage causes N1 and N2 to reverse direction, and V1 simulates off-hook, and at the same time starts V4 and V5 as IC 1— IC4 provides working power. At this time, the outside line can press the extension number, and the dialing signal is decoded by IC2 and IC3, triggering IC4, so that the output end of the corresponding extension is high level , the corresponding relay is engaged and the corresponding SCR is turned on, and IC5 and IC6 are powered to send out analog ring tone signals. The return line (prompts the dialing end that the call is connected) and the ring tone voltage are used for the extension to ring. If the incoming outside line does not know the extension number or does not press the extension number, after about 4 seconds, C11 charging ends and N1 outputs low level. N5 is prohibited from controlling the reset level of IC4, and the output terminal of N6 turns to high level, triggering pin 14 of IC4, causing pin 1 to output high level, J4 is closed, and the phone automatically connects to the host and rings. After the extension or host picks up the phone and picks up the phone, V8 is turned on and sends a reset level to IC4, all relays are reset, and the phone is connected to the outside line. After it is turned on, V3 turns on, N3 flips, discharges the power on C2, closes the analog off-hook circuit and releases the power on C11. Since the N1 output is high, N5 is allowed to control, and the high level of N5 output makes IC4 in Reset state, so there is no need to worry about the host relay being triggered and turned on by N6. When dialing an extension number, if you find an error, just press other numeric keys except 0~3 to reset IC4 and redial the extension number.

When the main extension wants to make an internal call, pick up the phone and turn on the power supply of IC1~IC4. If you press a certain extension number for a long time (the host number is "0"), the corresponding output terminal of IC3 will charge C6. After about a few seconds (according to the time constant of R8C6, adjust R8 to set the button press time to 2~4 seconds). The output of N5 flips to low level and the reset of IC4 is cancelled. Then the extension relay corresponding to the output end of IC4 is closed, SCR5 is turned on, and J0 is closed immediately, causing the 40V outside line to simulate off-hook, and prohibiting outside calls from being made. K0 switches to intercom call mode, and the called intercom phone rings to notify of an incoming call. If the called party picks up the phone, IC4 is reset by V8 and the ringing stops. If you want to make an internal three-party call, just press the extension number of the third party on any phone on the call (when the internal call is a third-party number, D8 is on and D22 is off, so there is no need to press the number for a long time), and wait for the third party to ring. After picking up the phone, the "three links" can be realized.

When dialing an external line from an internal line, just pick up the phone and dial like a normal telephone without an extension. Due to the functions of R8, C6, and D23, short-term dialing (such as the main extension number 0, 1, 2, 3 in the outside line number) does not cause the N5 output to change from high level to low level, and IC4 is always in reset, corresponding to the relay It won't close, SCR5 is also cut off, and J0 is not connected, so you don't have to worry about dialing the extension when dialing. After the internal line is hung up, V3 is cut off and the circuit returns to the waiting state. When the outside line calls the internal line without response and times out, R2C2 will limit the time to about 45 to 60 seconds and automatically simulate off-hook the internal line and hang up; if there is no response and the outside line hangs up before the set time is reached, IC1 will detect the callback from the outside line. Hang up busy tone signal, IC1 pin 8 outputs low level to hang up the internal line. Since the trigger voltage of D18~D21 is greater than 15 volts, when the extension is talking, other extensions will not be able to monitor it, which plays an effective role in confidentiality.

Assembly and debugging

1. The resistor marked as adjustable in the picture is finally installed. Connect the outside line of the telephone and the 9V power supply, and connect it to the extension. Use a 10K resistor to charge C2 from the positive line of the outside line. Measure and adjust R2 so that the conduction time of V1 is 45 after C2 is powered on. ~60 seconds.

2. Charge C2 again, adjust R21 to make the frequency of the phase-locked loop circuit IC1 consistent with the busy tone frequency (it must be debugged when there is a busy tone on the outside, otherwise it will be repeated). At this time, the voltage of IC 1 4 pins drops to 0V.

3. After picking up any phone, the V3 and V5 collectors should have a voltage of nearly 9V. Press other extension keys again and adjust R8 so that the key pressing time is 2 to 4 seconds before the base of V2 has a voltage of 0.6V. At the same time, the corresponding extension relay is also closed, and V6 should be turned on.

4. Connect a 2K resistor to R41 and adjust R41 to make the ringing sound loud and moderate. Measure whether there is a pulsating voltage at the collector of V8 after the extension with ringing sound is off-hook, otherwise replace V8. After debugging is completed, the wax-sealed adjustable components can be put into normal use. If there is no adjustable resistor that meets the specifications, you can use an external resistor for debugging, and then replace it with a fixed resistor.

Use and Maintenance The programmable control machine only starts the working power supply of most circuits when there is a call request. Normally, only N1~N6 (CD4069) are powered in standby mode, the current is a few μA, the consumption is minimal, and the power supply has a long service life. Therefore, it is very convenient and practical to use better quality dry batteries as power source.

During an internal and external call, if the external line wants to talk to another extension, the internal phone dials another extension number. After the two internal main extensions are contacted, hang up the internal call. The other extension only needs to press the hook once to communicate with the internal call. External line connection. If there is no answer from another extension, the original intercom phone only needs to flick the hook once to resume the previous call status.

Unless otherwise noted, the components are all conventional components and can be installed with miniaturized components.