[teh_klev]

> 64 Kbit/s ISDN leased line

That would have been Kilostream which wasn't part of the ISDN system. Kilostream pre-dated ISDN. The reason for its high cost was that you could throw as much data as you wanted to 24hrs a day and it was a point to point dedicated circuit, i.e. you couldn't "dial up" different locations the way you could with ISDN.

[adamretter]

@teh_klev That's interesting. I thought I also remembered the DSU being branded with BT ISDN logo, but perhaps I am mistaken, it was a long time ago now!