Audio – Alarm

Here is a simple IR audio link that can be used to transmit audio signals up to 4 meters. The signal to be transmitted is applied to the base of Q1 via resistor R4.The transistor Q1 drives the IR transmitting diodes D1 and D2.The audio input will be modulated to the IR signals transmitted. The [...]

Here is a simple circuit that will produce a musical horn when ever your car is in reverse gear.The circuit uses two ICs for the operation ,voltage regulator 7805(IC1) and musical tone generator UM66(IC2).The IC1 reduces the car battery voltage to 5V.The diodes D1 & D2 in combination produces an additional drop of 1.4 V [...]

Here is the circuit schematic of a simple audio surveillance system in which the transmitter will pickup sound from one location and the receiver at other location will reproduce it. The receiver and transmitter are connected by only one set of wire. Here both power supply and transmitted signal share the same wire. The audio [...]