Simple Telephone Ring Tone Generator Circuit

This is the figure simple telephone ring tone generator circuit designed using only a few components. It produces simulated telephone ring tone and needs only DC voltage (4.5V DC to 12V DC). One may use this circuit in ordinary intercom or phone-type intercom. This is the figure of the circuit;

The sound is quite loud when this circuit is operated on +12V DC power supply. However, the volume of ring sound is adjustable. The commonly available 14-stage binary ripple counter with built-in oscillator (CMOS IC CD4060B) is used to generate three types of pulses, which are available from pin 1 (O11), pin 3 (O13), and pin 14 (O7), respectively. Preset VR1 is adjusted to obtain 0.3125Hz pulses (1.6- second ‘low’ followed by 1.6-second ‘high’) at pin 3 of IC1. At the same time, pulses available from pin 1 will be of 1.25 Hz (0.4-second ‘low’, 0.4-second ‘high’) 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.

Simple Single Cell 1.5V Hearing Aid Circuit

This is a hearing aid circuit with 1.5v supply. This circuit is used to detect very faint sounds, then deliver the sounds to an 8 ohm earpiece. This circuit requires 1.5v input voltage, need only a single cell battery. This is the figure of the circuit;

This circuit can be assembled in a small board, or you can even do it without board. To assemble without board, you can connect every component leads each other and solder them. Align the component bodies and their leads to avoid shorts, secure with insulation tape, glue, or resin.

Simple Signal Injector Circuit

This is a circuit for signal injector circuit that is important tool for troubleshooting your electronic circuits. As an example, this circuit can be used to test amplifier circuit. This is the figure of the circuit;

This circuit also a lot of harmonics. By connecting the ground clip to the 0v rail and move through each stage, starting at the speaker, the fault in an amplifier can be found. At each preceding stage, the volume will increase. This circuit can inject FM sound sections in TV’s and the IF stages of radios.