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Using this schematic can be made a network voltage indicator electronic circuit. If the input voltage is present across the network, the optocoupler transistor is open, T1 is blocked and controlled rectifier, Th1, is in a state of conduction. Since both terminals of the piezoelectric buzzer is at the same potential, buzzer is off. If voltage disappears, the transistor T1 enters the conduction and thus makes the terminal of buzzer to be put on the ground (maintains thyristor conduction state).  Network Voltage Indicator Circuit diagram: In this situation, there is a sufficiently large potential difference across the buzzer and D5's to determine that these two elements to indicate AC power loss, both audible and visual. By pressing the reset button current is interrupted by Th1, so thyristor enter in blocking state and the other terminal of the buzzer is connected to ground.

2.4 Occupational Information Review Exercises 1.         List the four branches of an electrical and electronics engineering field. 2.         For each branch of electrical engineering named in  question 1  above, describe briefly its operations. 3.         State why are licenses required in installation work by private contractors? 4.         List any five companies which are involved in the field of communication engineering. 5.         Define the following terms as applied in electrical engineering occupations: a.         Artisan. b.        Craftsman. c.         Technician. d.        Engineer. 6.         Describe briefly the educational req...

Using this schematic is created a network voltage indicator electronic circuit. If the input voltage is gift across the network, the optocoupler transistor is open, T1 is blocked and controlled rectifier, Th1, is in a very state of conduction. Since each terminals of the piezoelectric buzzer is at identical potential, buzzer is off. If voltage disappears, the transistor T1 enters the conduction and therefore makes the terminal of buzzer to be placed on the bottom (maintains thyristor conduction state). during this state of affairs, there's a sufficiently giant potential distinction across the buzzer and D5's to see that these 2 components to point AC power loss, each audible and visual. By pressing the reset button current is interrupted by Th1, therefore thyristor enter in blocking state and therefore the different terminal of the buzzer is connected to ground. http://streampowers.blogspot.com/2012/07/sp-network-voltage-indicator.html 

Like all its counter Parts, this network wiring tester comprises two elements, a transmitter unit, powered and fitted at the network start point, and a receiver unit, passive, which can be moved around from socket to socket. Each of these units carries eight LEDS, identically labelled 1 to 8. By operating a push-button in manual mode, or using a clock in automatic, the eight LEDs light up in sequence on the transmitter unit and obviously they should do the same on the receiver unit. In this way, just by watching the LED lighting cycle on the receiver unit, you can immediately spot any crossed wires, as well as any open circuits (the relevant LED never lights up) or shorts (two or more LEDs light at the same time). Circuit diagram : Network Wiring Tester Circuit Diagram The transmitter unit circuit is simple' The Schmitt-input NAND gate lCl.A is wired as a multi-vibrator, whose speed can be adjusted using Pl, while lCl.B is wired as a simple debounce circuit for button 52, used...