There are 4 cards, collectively known as Digital Tachograph cards, that are used by the Digital Tachograph system:
The company card is a plastic card similar in size to a photo driving licence/credit card, with a microchip in it.
Like the analogue Tachograph, the digital unit records driver activity times - driving, other work, rest and breaks. However, unlike the analogue, which records only to a record sheet, the digital units record to the driver smart card and also hold the information in the Vehicle Unit (VU).
The card will allow you to download information from the VU in order that you can carry out checks on drivers’ hours and rostering etc as required by the legislation, and to maintain records described in the undertakings of your Operators’ Licence issued by the Traffic Commissioner.
Digital Tachograph Card Application form from the DVLA: http://www.dft.gov.uk/dvla/onlineservices/order_forms.aspx
Source: Transport Office