TalkTalk has begun trialling its Multi-Room TV service, which is set to be launched commercially in spring.
The new service will let customers watch TV on up to four devices at once when it goes live, while using the same account.
Compatible devices include laptops and desktop PCs, as well as iOS and Android phones and tablets, while people will also be able to use Google Chromecast to stream content from their phone to their television set.
To take advantage of the service, customers will pay an additional - and as yet unconfirmed - monthly fee, in exchange for a second set-top box that is placed in another room.
Households will be allowed to have two boxes at most, although TalkTalk has not ruled out increasing this number if there is sufficient demand.
According to ISPreview.co.uk, the set-top boxes are now being rolled out to those who signed up to trial the service late last year.
Because the Multi-Room service works as a boost, customers can cancel it one month, and not have to pay for it, then reactivate it later on.
This means that they will be unable to use the second box in the months they are not paying for it.
In a trading statement in November last year, TalkTalk confirmed that it planned to launch its Multi-Room service in the first half of 2018.
This, it said, would allow the company to "address a new segment in the market", with its multi-screen platform offering "consistent access to Video On Demand and linear content, complementing the YouView set-top box experience".