Channel 4 HD has reportedly begun test transmissions on Freeview HD ahead of its forthcoming launch.
As spotted by members on Digital Spy's Freeview forum, Channel 4 HD is now transmitting a test caption on high definition digital terrestrial television.
The broadcast was reported by a member in the Crystal Palace transmitter area in London, and confirmed by a member in the Granada TV region covered by the Winter Hill transmitter group.
Another member also reported the test transmission from the Emley Moor transmitter area, which began receiving Freeview HD broadcasts this month from an advance network.
Channel 4 HD will be Freeview HD's third available channel, following the technical launch of BBC HD and ITV HD last December.
However, Ofcom recently confirmed that Five HD will not launch on Freeview HD as planned this year, with the available capacity reverting to the BBC.
