Sonsivri

Hi,

How i can obtain 48V from 12V or from 5V PSU?  i am trying to emulate telephone line for testbench

Hello,

it is possible to produce 48v with 12v,

you can use MC34063 in mode Boost, you need only few components, inductor, diode, capacitor, some résistors.

The 48v is stabilized with MC34063.

The datasheet for MC34063 is easy to find with google.

Bye.

I think 48V is not enough for telephone lines. When ringing, the voltage rises to aprox. 90V.
You can use a small transformer ( 4 - 10W ) and osilator for generating 48V and another one for ringing voltage ( 4W ).
 

For practical purposes, you could use a disposable camera flash inverter to produce the 90V required.
You can regulate the voltage with a zenner. Remove the capacitor before use!!

Par.

PS. How are the holiday Jeanine?

only for emulate line not ring.

I dont need ring for my evil purposes :)

I've used just one or two 9-volt transistor batteries in series to emulate a phone line. Very simple for anyone to do. I wanted to connect a fax machine to a computer fax/modem to send and receive test faxes. Worked great.

Are you sure=?


i need the line voltage to transfer an incoming cellular calling from handsfree to my home telephone....

No, I'm not sure. Maybe aliens implanted those memories in my head!

Referr to the simple schematic here:
http://www.jagshouse.com/modem.html

You asked how to "emulate telephone line for testbench." I provided a quick and simple solution and told you I had used the same circuit with complete success.

You can do it with batteries as suggested by other people before.  It is a good advice to use a series resistor of 470-680 Ohms with your source, battery.
You can also use a small transformer (as also was suggested before) of around 30V AC and rectify it to take DC out.  Use an electrolytic cap to smooth the voltage and a series resistor of 470-680 Ohms.

Even two batteries of 9V will do the job fine.  It is a rare case that an equipment may need voltages as high as 48V, most telephones, faxes, modems may work with lower voltages.

But I suggest to always use a series resistor.  This will minimise the loop current and will lower the off-hook voltage arround 10V.

            + ________/\/\/\/\________   
Your source           470-680Ω
here.                                                   Your equipment in this side

            - ______________________

                 

Well

i need to conect a telephone with this "line" and connect to the mcu board that is connected to a cell phone.

9V will be enough?  i thought that 48V was the level!

pl4tonas told you two 9V batteries would work and provided a very good method of establishing a working telcom current loop that can be used for voice and data. I can confirm it works well because I personally did it a few years ago.

Why don't you go back to the source who told you 48 volts were required and ask them to help you because you're certainly not believing a word any of the forum members tell you.

Frankly, I'm starting to suspect your elevator doesn't go all the way to the top.

LOL so funny,

The reason 48V was used by telephone co. was the volt drop on long lines.
at you phone 24v to 48v on hook, about 8v to 11v off hook.