Produced using this phone detector circuit that can accurately determine and eliminate telephone ringing circuit, the call circuit and dial-up circuit failures, easy to use.
The unit power circuit and ringing, the call part of the detection circuit shown in Figure (a) below. Power from the 220V AC power supply by the transformer Tl, the output sub-divided into two groups. A group 9V AC, the rectifier diode VD3 ~ VD6, capacitors C6, C7 filter, three-terminal voltage regulator IC2 block, output 5V DC, for the power of the machine for testing. Another group of output is 50V AC, some by the resistance Rl, capacitor Cl limiting, blocking, for the ringing circuitry; another part of the diode VDl by the rectifier, filter capacitor C2, resistor R2, R3 limit for delivery, then If detected by the circuits. Will be measured using the phone with the machine terminals L, M connection, power switch Sl is closed connected to 220V AC power, the dialogue machine can be ringing, the call and dial the three were part of the circuit for testing. Detection ringing circuit, the phone is on-hook, the toggle switch s2 position allocated to the ring, then L and Z phase, the current limit, blocking the AC by the M, L-ended output, into the phone under test , provides power for the phone ringing circuit. Such as the telephone ringing circuit under test works properly, you can hear the phone ringing. Detection of sub-circuits by the call circuit and transmitter circuit, then test in two parts. Tested the phone is off-hook state, so that toggle switch S2 in the call, dial position (N). At this point, the phone and the machine M, N terminal phase. Adjustment potentiometer RPl, so that the light-emitting diodes as the light has just lit LEDl. If the circuit under test signals provided by the music Manifold ICl, when the key switch S3 is closed, ICl may trigger a very TG electricity, music block is triggered work. Music signal output by the end of ICl's OUT, the transistor VTl such amplification, fed into the phone. If the machine is working by the words of the circuit, a wonderful blend of music begins with the handset or hands-free speaker phone in the spread, while light-emitting diode LEDl flashing the rhythm with the music. Detection of transmitter circuit, gently tapping or blowing phone hands-free microphone or a microphone, the resulting audio signal input by phone from the capacitor C4, through the transistor VT2 ~ VT4 third place too, the output from the light-emitting diode LEDl . If the circuit to send a normal phone, with the percussion signal input, the rapid light-emitting diode LEDl, its brightness with the percussion signal strength varies. At the same time, handset or hands-free speaker will issue a "giggle" or "Hu Hu" sound.
Figure (b) as a dedicated dial-up circuit detection circuit, figure, IC3 is DTMP (dual tone multi-frequency) signal receiver decoding Manifold CM8870, it will be issued two-tone telephone dial tone signal reception and translated into BCD code, the IC4 decimal counting / pulse divider CD4017 sent to the decoder driver IC5 block CD4511, by the common cathode LED display directly dialed phone number. Pulse dialing, receive and display is IC6 (NE555), IC8 (CD4518), IC4 (CD4017), IC5 (CD4511) and digital together to complete the. When the phone dialing in the pulse, a pulse for each input signal, after shaping IC6, IC8 the ? feet from the input, the count and the output into a BCD code, into the IC4, IC7 assigned to the IC5 decoding, and finally by the digital display the phone dialed number. Detection of dial-up circuit, toggle switch S2 set the call, dial position (N), potentiometer RPl detect the position and the location of the call the same circuit. Pulse (P), two-tone (T) switch S4 should be consistent with the phone under test. The circuit of pulse phone (including the old-fashioned dial phone) and dial-tone telephone circuit can be tested. When tested to dial the phone, if the machine is normal dial-up circuit, the unit will have a direct digital display of the dialed number, while light-emitting diode LEDl struck with the number and shiny.