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This is a newer version of previous device. This one can have up to 6 relays and 6 sensor-state inputs. The task was to build a device that connects to the phone line and has a relay as an output switch. It should also sense if the connected  «consumer» is turned-on or off and report to the administrator at the other end of the phone line. The administrator would then call-in the device, log in with the password, and check the state of  «consumer», turn it on or off, change password or some other settings. Download : Schematic, Program files And Documentation Schematic: Full Schematic Telephone operated remote control

Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and is therefore a good, useful beginner project.   Circuit diagram Parts R1 180 Ohm 1/4 W Resistor R2 12K 1/4 W Resistor C1 330pF Capacitor C2 12pF Capacitor C3 471pF Capacitor C4 22pF Capacitor Q1 2SA933 Transistor D1, D2, D3, D4 1SS119 Silicon Diode D5 Red LED S1 SPDT Switch L1 Tuning Coil MISC Wire, Circuit Board Notes 1. L1 is 7 turns of 22 AWG wire wound on a 9/64 drill bit. You may need to experiment with the number of turns. 2. By stretching and compressing the coils of L1, you can change the frequency of the transmitter. The min frequency is about 88 Mhz, while the max frequency is around 94 Mhz. 3. The green wire from the phone line goes to IN1. The red wire from the phone line goes to IN2. The green wire from OUT1 goes t...

With the aid of an (old) moving coil instrument it is very little effort to make a simple voltmeter that, at a glance, indicates the status of a telephone line. Because the input impedance of this circuit is very high, there is no problem in having it permanently connected to the line, since it only draws a tiny amount of current. The schematic shows that the circuit consists of no more than a series resistor, a bridge rectifier and a moving coil meter. The value of the resistor depends on the sensitivity of the moving coil meter. In his prototypes, the author used old VU meters that require 250µA for full-scale deflection. A resistor value of 390 kΩ appeared to be optimal for these meters. Telephone Line Indicator Circuit Diagram For a 100-µA-instrument, this resistor value will have to be increased to about 680 kΩ. The starting point, when selecting a resistor value is that when the telephone is not in use, the meter should deflect about 2/3rd of full scale. The amount of meter defl...

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...