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A number of firms have shown off smart doorbell products at CES, aimed at the growing smart home security market.

Amazon-owned Ring's Door View Cam can be attached via an existing peephole in a door. The firm told the ������̳ it was aimed at renters who may not be allowed to drill holes in a door.

It also has a sensor which notifies you if someone knocks on the door instead of ringing the bell.

French firm Netatmo is offering free video storage with its new product.

Other firms tend to charge a subscription to store video captured by a doorbell device.

The Netatmo Smart Video Doorbell is fitted with a microSD slot to store video in an encrypted form, but it can also be transferred to a Dropbox account or another server.

It works with Apple's HomeKit system, as well as Android and web applications. However, unlike Ring's device, it requires wiring.

More from CES 2019:

California firm Maximus unveiled a doorbell which contains two cameras to provide a broader field of vision.

Smart smoke-detector maker First Alert announced its first smart doorbell system, the One Link Bell, which it said would also work with both Amazon Echo and Google Assistant smart speakers.

Industry analysts Futuresource Consulting estimated that nearly 110 million smart home devices were shipped worldwide in 2018.

"Not only is the security and monitoring segment shipping in high volume, it also boasts the highest average prices per unit," said Filipe Oliveira, market analyst at Futuresource Consulting.

"Our forecasts suggest it will be knocking on the door of $10bn (£7bn) in trade value for 2018. Penetration rates will continue to climb, with 7% of homes worldwide having at least one smart security device installed by 2022."

Read and watch all our CES coverage at bbc.com/ces2019