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This circuit will allow you to connect any tape recorder that has a mic and remote input to a phone line and automatically record both sides of a conversation when ever the phone is in use. You will need to take a couple of voltage readings before connecting the circuit. First determine the polarity of your phone line and connect it to the circuit as shown and then determine the polarity of the remote input and connect it to the circuit. Circuit operation is as follows. When the phone is on hook the voltage across the phone line is about 48volts dc. When the phone is off hook the voltage will drop to below 10volts dc. When the line voltage is at 48volts the FET is off which causes Q2 and Q3 to be off. When the phone is picked up the FET turns on along with Q2 and Q3 which turns your recorder on. The tape recorder must be in the record mode at all times. As you can see the power source for the circuit is the phone line. Circuit Diagram

This circuit provides secrecy when two or more telephones are connected in parallel to a telephone line. The circuit also prevents incoming calls to as well as outgoing calls from other telephones connected in parallel, except from the one lifted first. When someone picks up the handset of the telephone connected in parallel to the original (master) phone for making an outgoing call, no dial tone is heard and the phone appears to be dead. But when a call comes, the ring signal switches the SCRs ‘on’ and conversation can be carried out. As soon as the handset is kept on the hook, the SCR goes off and the telephone can again only receive incoming calls. Parallel Telephone with Secrecy and Call Prevention Circuit Diagram When a call comes, conversation can be made only from the telephone which is lifted up first. To carry out conversation from the other telephone, the handset of the telephone that was lifted up first has to be placed on the hook and then the push-to-on switch of the assoc...

This circuit enables  automatic switching-on  of  the  tape  recorder  when  the  handset  is  lifted.  The tape recorder gets switched off when the handset is replaced. The signals are suit-ably  attenuated  to  a  level  at  which  they can be recorded using the 'MICIN' socket of the tape recorder. Points X and Y in the circuit are connected to the telephone lines. Resistors R1 and R2 act as a voltage divider. The voltage appearing across R2 is fed to the 'MIC-IN' socket of the tape recorder. The values of R1 and R2 may be changed depending on the input impedance of the tape recorder's 'MIC-IN'  terminals.  Capacitor C1 is used for blocking the flow of DC. The second part of the circuit controls relay RL1, which is used to switch on/off the tape recorder.A  voltage  of  48  volts  appears across  the  telephone  lines  in on-hook  condition. This  voltage drops  to  about  9  volts  when  the handset  is  lifted.  Diodes  D1 through  D4  constitute  a  bri...

Telephone Ringing circuit Diagram . Even though cordless phones have invaded our homes and offices, you don’t always have them at hand, and as their ringtones are usually very much quieter than the old rotary-dial- type analogue phones, it can happen that you miss a call you’ve been waiting for while you’ve been going about your daily business.  Until quite recently, you could still find remote ringers that could be plugged into any standard phone socket in order to have an additional ringer, but it seems as if these accessories are currently being phased out as everyone is ‘going cordless’. So we decided to suggest something better, with this phone ring repeater that makes it possible to control any device connected to the AC power outlet using the ringtone available on any subscriber line, and naturally, with all the guarantees of safety and isolation that are of course rightly expected. So it’s capable of driving a ringer, or indeed even a high-powered sounder to alert you when ...

This below circuit is a easy handsfree telephone receiver system.  This doesn’t have dialing circuit so, it’s not a total phone replacement  circuit, but it’s just only a loudspeaker system (i.e, phone  receiver,not dialer). This is a easy circuit with all parts easily  available, and without any complex I.C. It is made of just capacitors,  diodes, resistors, and transistors.  This circuit can be made within 70  rupees and it compromises of the following sections  Loudspeaker Circuit For Telephone Circuit Diagram   Power rectifier and filter section  This section is made of a simple bridge rectifier and a indicating power LED. Voltage regulator section This section is made upon transistor Sl100, which is a general purpose NPN transistor in metal package. That is used to regulate voltage at a level of 9+0.6=9.6V by a 9V zener diode. Speaker output section This section contains a high impedance speaker and two BC548 NPN transistor to ampl...

This is a simple home telephone ringtone generator circuit which is built with applying only several electronic components / parts. It generates simulated telephone ringtone and requires only DC supply with 4.5V DC to 12V DC voltage. One may possibly use this circuit in ordinary intercom or phone-type intercom. The sound is pretty loud when this circuit is operated on +12V DC power supply. Even so, the volume of ring sound can be adjusted. Telephone Ringtone Generator Circuit Diagram CD4060B is chosen to produce three kinds of pulses. Preset VR1 is fine-tuned to get 0.3125Hz pulses at pin 3 of IC1. At the same time, pulses obtainable from pin 1 will be of 1.25 Hz and 20 Hz at pin 14. The three output pins of IC1 are connected to base terminals of transistors T1, T2, and T3 through resistors R1, R2, and R3, respectively. Working with a built-in oscillator-type piezobuzzer generates about 1kHz tone. In this particular circuit, the piezo-buzzer is turned ‘on’ and ‘off’ at 20 Hz for ...

This design controls up to 8 devices using a PIC microcontroller (PIC16F84A) connected to the phone line. The unique feature here is that unlike other telephone line based remote control, this device does not need the call to be answered at the remote end so the call will not be charged. This device depends on number of rings given on the telephone line to activate/deactivate devices. Set the DIP SWITCH as follows: Switch RA4     Switch RA3        No. of initial rings to Switch ON(activate half of the board) OFF        OFF             2 ON         OFF             4 OFF        ON              3 ON         ON              5 T...