If you're thinking about buying a baby monitor, here's what you need to know.

How they work

Baby monitors are one-way intercom systems that transmit using radio waves. They have a transmitter (baby unit) that's placed near the baby and a receiver (parent unit) that you keep nearby.

You plug them in, make sure both units are set to the same channel, switch them on, and adjust the volume on the parent unit to a level you can easily hear.

A baby monitor is a useful back-up - but it doesn't substitute for normal care and supervision. Silence might be bliss but it can also be an alert to go and check your child.

What to look for

• Number of channels is important. There should be at least two frequencies. Technology that uses digital enhanced cordless telecommunication (DECT) stops interference from other baby monitors or cordless phones.
  
  
• Battery operation on the parent unit means you can carry it with you around the house. A battery on the baby unit is also useful where there's no mains power (for example if you go camping).
  
  
• Automatic battery back-up is useful in areas where power cuts are common.
  
  
• Battery-condition indicator warns you when the battery is low.
  
  
• Light display allows you to "see" your child's cries on the parent unit. It's good for when you have visitors or are watching TV: simply turn down the volume and make sure you can easily see the unit.
  
  
• Night light on the baby unit gives a soft glow which may comfort the child and helps you see better in a darkened room.
  
  
• Belt clip lets you carry the parent unit around the house and outside.