Or you could go with the ultimate in cheap and easy:

I live on rent in a house at the first floor with a common main gate. The house owner's and our guests, both, knock at this gate! So what i wanted was a camera installed on the main gate and connect it to a display screen in our sitting lounge!

This device would've been great if our home were on ground floor or my guest knocked on my door directly. So it is of little use to me

Oh. I was a little confused. You said front door.

There are lots of inexpensive systems available. They even go cheaper than this.

http://www.ezwatch.com/ezbullet-vf-platinum-1.html

Sir i want to make a mini project out of the need i have! can i use a webcam and connect it to a lcd screen? or use a camera with analogue output?

Yes. The internet is loaded with DIY security/camera systems. All you have to do is find one that will work for you, and install it.

http://www.ehow.com/how_6734687_diy-security-cell-phone-alert.html

This sounds like a description of my weekend...

The panel burned at our family lake cabin...we're re-wiring the entire house.

The boys enjoy learning new words when Papa has a project going.

Can i connect my mobile phone's 5megapixel camera to an lcd screeen?

or use a webcam instead?

http://www.screwfix.com/p/kit-video-b-w-hands-free/66285

I think he wants to build his own camera from sticks and twigs and stuff you find along the road.

Actually it's going to be way cheaper to buy one than build one...even if you are an electronic engineer....economy of scale and that sort of thing. They can sell you something retail for less than you could build one of for that reason...and its likely to work a lot better as they will have sorted out all the little naggy things you won't even think about until they happen.

Been there, done that.......now I rent the movie.

I've got an Airlink 101 at work. (Not an endorsement) I have the luxury of having it hardwired into my server, but you can run it wireless if you want to.

They're about $100.00USD.

KJK/USA has a system, he can give you better advice than I can.

You have many IP camera options.

Google "IP Camera"

Depending on what you consider "cheapest", the two types I use are:

First - Linksys WVC54GCA Fixed.

Cost two years ago - $100.00 (US)

Second - LevelOne WCS-2060 PZT

Cost two years ago - $ 460.00 (US)

I can access these cameras from anywhere on the planet with a few clicks of the mouse on my laptop.

For instance, I am 70 miles from home right now sitting in an office. Three mouse clicks on my laptop and I am watching live video of my home (images above).

You can also arm any pixels for motion alarm and you can program these cameras to send you an e-mail video of what tripped your alarm.

These cameras have built in mini servers. All you need is a DSL (always on) line and a wireless router if you want to connect wirelessly on the camera end. Both cameras can be hardwired also.

Check out Tigerdirect.com - This is a great company that I have bought electronics from for many years now. They have a nice IP camera selection.

I'm confused again.

Does the OP want to do this themselves or do they want us to do it for them?

Harbor Freight

http://www.harborfreight.com/catalogsearch/result?q=security+camera

You can search for 'bullet camera' on the internet. Many of these are waterproof. I have a wired one, the cable is about 100' long, you might can go somewhat longer with an extension. It uses a wall wart for power, then you get a composite video and audio output. I plugged it into a cheap B&W TV from RadioShack. If you have a TV with composite input in your sitting lounge, you could use it and switch the picture to the composite input when you hear the knock.

phoenix911 has listed a link for one bullet camera from harborfreight.com

http://www.harborfreight.com/weatherproof-security-camera-with-night-vision-47546.html

i need a camera like this one!.. which can be easily plugged to any lcd or even a tv!... note the type of output pins the connector has!.. what is a wired output format like this called?? and what are these type of cameras called?

RCA audio and video jacks, you can buy a converter (china) that plugs into your usb port. they are about $20.00.

As the title says, this is a security camera. The night vision (0 lux) aspect is produced by the infrared LED halo array around the lens. This implies to me that this will also reach into the infrared region for imaging, a useful feature for a security camera. The single RCA video plug (yellow) implies that this is a composite video output signal, likely NTSC due to the 120VAC 60HZ connector on the power supply brick. Security cameras are the last bastion of this formally ubiquitous video format. Because of this, it can no longer be plugged into any monitor or TV because digital TV is now the broadcast standard. Since digital TV is relatively new, there are many monitors still available that can take composite video signals too. Look for monitors that have the mate to this RCA plug on their chassis. There are also many composite to digital adapters available that will allow this signal to be displayed on a digital screen.

Since this camera has a built in microphone and as you said earlier you intend to use this at an entrance, you might want to run an intercom system along with these cables so you can talk with your visitor.

Have fun, be safe.

This is a picture of what i want!.. Does this rca connector wire allow us to connect the camera directly to a tv or a compatible monitor and get a display when ever i swith to the AV mode in the television?

There are cheap color cameras with a 2.4GHZ transmitter built in and a downconverter. Provided you can still can receive UHF signals on your TV, tune a channel to that camera, switch TV channels when you hear the gate go......

I use several that I bought in the USA as a rear view mirror when pulling my caravan. They work on all the TVs I have ever had....the mini TV I use in the car is only B/W.

These are the ones, you could keep one set and sell the others......final offer!!

http://www.x10.com/promotions/xx32a_says_goodbye_camera_system.html?HP2

http://www.harborfreight.com/black-and-white-security-system-with-two-cameras-monitor-66556.html

Really neat!!!

I just became a grandfather, and the baby's parents bought a wireless baby room monitor with video and two-way audio.

Probably not protected from the environment, just another suggestion.

Or protected from your neighbors listening in to what you say within its range....if there is any kind of density and your neighbors aren't 50 feet or less away.

Oh trust me...the things you can hear on these things if you are in range. BESIDES the rugrats.

Right you are! I forgot about that "issue".

Had that problem myself and we live on 1/3 acre.

We kept hearing voices that weren't coming for our house.

How about purchasing a rear view camera from a Auto Salvage yard and installing it using a plug in 12 volts power supply ?