I can hear them on video chat but they cant hear me

To help you troubleshoot the issue about Facebook video chat while you are speaking up but the person on other side is not able to hear your voice. Follow the steps given below to make sure your microphone is working:
- You must have a built-in microphone or external microphone to chat. If you notice that your microphone isn't working and you're not being heard, check your microphone to ensure it's properly plugged in, not muted and configured as the default microphone source.
- Plug the external microphone all the way into the correct socket on your computer. This socket is often located in the front of the keyboard or on the back of the computer and depicted by the shape of a microphone.
- Toggle the headset's mute switch to the off position if it has one.
- Press 'Windows' key + 'R' key on your keyboard.
- In the Run box type 'Control Panel' and hit Enter button.
- Click on 'Sound' Click the 'Recording' tab of the Sound window. Click the 'Microphone' that you wish to use from the list of available microphones and then click 'Set Default' and Click OK to save your settings and begin using your microphone.
- Log in to Facebook. The Facebook Chat feature appears along the right side of the Facebook homepage with a list of your friends. Friends with green dots next to their names are available to chat. Click the name of the person you wish to chat with. A new window appears as a video camera icon in the upper right corner. Click the video camera icon. When prompted, download and install the Facebook Video Call Setup.exe file. A call is placed to your friend. Your friend then must click 'Accept' to accept the video chat. Once he does, speak into your microphone to test it.

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Make sure have installed the drivers for microphone http://www.driverscape.com/manufacturers/acer/laptops-desktops/aspire-5315/619