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Hi, I have an image of the transformer and I need to understand the data written on it. It seems to have three secondary windings. Here is the photo: What does this S1+S2=15V? Is the 15V shared between these two windings or is it the voltage rating for an individual winding? Is it same for the current rating as well? Thanks.

Thanks Arun for your time. I have already implemented over current protection circuit but I am going to use regulator circuit as well. Thanks.

Hi, I am almost done with designing the PCB. But one more question I want to ask is: Should I directly connect the battery to the modem or is there a need of any isolation or some kind of protection circuit required; like current limiting. Any suggestion will be appreciated. Thanks.

Thanks a lot Hero999. I am going start this project as soon as possible. Thanks again for helping.

Thanks Hero999 for your quick response. Although I posted a few links but I am not sure whether these circuits are really reliable. I mean as I am new to electronics I don't know whether these really are the circuits to start with. If they work perfectly then I am going to start my project. Thanks.

Did I post the question in the wrong forum????

Hi Sir, I am quite new to electronics. I have a modem (from Teracom) powered by 12v(DC) 1.5Amps adapter. I want to run this modem using a 12v battery which needs to be automatically charged using 230V 50Hz AC power. I came across many schematics when searching on the internet. Following are the two links I think we can start with: http://www.circuit-projects.com/battery/charger-circuit-for-6v-or-12v-car-battery.html http://electronicsuite.com/power-supply-2/12v-car-battery-charger-suite/#axzz1QP3aTqRg I have a 12V 4.5Ah battery. Can you please help me start designing the circuit? Thanks.

I got it. Thanks Hero999

Thanks Hero999 for your quick reply. Of the following four options what will you choose? 1) 0.5A 2) 1.0A 3) 2.0A 4) 3.0A I was asked this question during placement exam and I marked 2A giving the explanation that voltage will drop until the value of current is reduced to 2A. Am I correct? Thanks again.

Hi, I have one question. Suppose I have 24v/2a DC power supply. If I connect 8 ohm resistor across this power supply what will be the current flowing through the resistor? And on what factors does the maximum current of power supply depend?

In my initial post I said I want to get rid of wireless headphones. My goal is to aim a sound signal at a particular point without anybody in the area hearing it.

I myself couldn't find enough relevant information. But I did find a link. http://www.explainthatstuff.com/directional-loudspeakers.html See if that can help. Thank you.

I want the device to transmit within 7m. Basically I want to get rid of earphones. I don't want it to be so much powerful. I just want to use it at home for entertainment purpose. I don't want to disturb my neighbors when I am on loud music. I actually saw this system working in a disco where sound was 'embedded' in beams of light. I assume this works on the same principle.

Hi, Can somebody help me with the circuit to produce directional sound. I read somewhere that ultrasound of certain frequency acts as a carrier wave and the information is the modulating wave. But I couldn't find the schematic. Is it much like the same as producing AM or FM?