telephone ringtone generator
No description available.
auto answering circuit
This circuit is not highly critical and can utilize various devices (such as a tape player with a message recorded on an endless tape) that do not overload the circuit or the telephone line. The incoming line is safeguarded by...
Simple Telephone Transmiter
This circuit diagram represents a simple yet effective transmitter circuit, capable of transmitting telephone conversations. When the telephone receiver is on the hook, the line voltage is approximately 48 volts. The R7 preset resistor is adjusted to achieve a voltage...
Basic RF Oscillator circuit diagram
Experimenting with the size of the coil and the number of turns can influence the frequency and signal output of the oscillator. The signal can be received using a standard FM radio receiver. The input signal should be coupled via...
Marker-generator
The oscillator section employs three sections of a 7400 quad NAND gate integrated circuit. The 1 MHz signal generated by the oscillator is input into a 7490 decade counter, which is configured to divide by ten, producing a 100 kHz...
Telephone call meter circuit
In this circuit, a simple calculator, in conjunction with a COB (chip-on-board) from an analogue quartz clock, is used to make a telephone call meter. The calculator enables conversion of STD/ISD calls to local call equivalents and always displays current...
Colpitts oscillator FM transmitter
Its frequency depends on the capacitance of the vary cap diode. The center frequency is changed by varying the biasing voltage of the vary cap through the 47K pot. You can use a 75cm telescopic antenna or simply a length...
Simple triangle-square wave oscillator
By making Rt variable, it is possible to alter the operating frequency over a 100 to 1 range. The versatile triangle/square wave oscillator has a possible frequency range of 0 Hz to 100 kHz.
The described circuit features a variable resistor,...
Metal detector circuit diagram 3
The metal detector consists of a probe oscillator, a reference oscillator, an audio amplifier, and various other components, as illustrated in the schematic. The probe oscillator is made up of transistors V1 and V2, a detection coil L1, a capacitor...
Metallic pipe detector
This circuit employs a 15-kHz oscillator coil. When metal is removed from the energy field, the oscillator voltage is rectified and compared to a reference. A decrease in oscillator voltage activates comparator IC2, causing D4 (LED) to turn off.
L1 consists...