CityVision Bullring is a 5.76 metre high by 3.84 metre wide portrait display positioned on the approach to the Bullring Shopping Centre near to the centre's Selfridges store.
It is the first of eight sites Signature is aiming to have in place by next March as part of a 10-year contract awarded to them by Birmingham City Council.
The CityVision project will involve digital signage in portrait, 96-sheet and 48-sheet formats at gateway sites in the city centre.
Advertisers using CityVision Bullring are Coventry University, booked by MJD Consultancy, Channel 4, booked by Posterscope, and Thomson Holidays, booked by Kinetic.
James Harrison, sales director at Signature, said: "CityVision will create an entirely new media channel in Birmingham, in locations that will take roadside digital to unprecedented levels.
"We'll be able to inform and interact with consumers in a way that will truly revolutionise OOH in the city and is the logical progression from our current position as the largest owner of backlight sites in Birmingham."Follow @nickbatten2