All modern Bang and Olufsen Beolab active speakers (ie. those powered from the mains supply) should be connected to your audio system or television using Powerlink cables. These are all similar in outer appearance, with a round 8-pin DIN plug at each end of the cable. However, there are three versions of this cable:-
Powerlink mark 1 is the simplest type and can be used by most Beolab speakers, including Beolab 1, Beolab 2, Beolab 2500, Beolab 4000, Beolab 6000 and Beolab 8000.
Powerlink mark 2 (also known as "fully wired") is for speakers with built-in displays, including Beolab Penta (mark 2 and 3 models only). This is also required for use with Beolab 5 speakers. This cable will also work with all other Beolab speakers with Powerlink connections, so it is the best version to choose if you are likely to change your speakers in future.
Powerlink mark 3 is the latest version for the ICE-Power Beolab speakers with class D digital amplifiers, as it contains an additional voltage reference wire intended to prevent background hum. This is for Beolab 3, Beolab 4, Beolab 7.1, Beolab 7.2, Beolab 9 and Beolab 10. This can also be used to replace mark 1 cable, so any of the speakers listed for use with mark 1 cable can also be used with mark 3 cable.
All three types of Powerlink cable are available from Bang and Olufsen. eBay shops such as Sounds Heavenly also produce cables which are compatible with mark 2 and mark 3 Powerlink speakers.
The exception to the rules above are the very earliest Beolab speakers (mainly the Beolab Penta mark 1), which used a special connection type called Speakerlink. This used a specially made plug, which has not been available since the late 1990's. However, a 2-pin DIN speaker cable can be used to power these speakers, although the displays will not light up.