In message ,
Tom Anderson writes

I was having a lot of trouble with mine, getting 70 and 71 errors. I keep
mine in my general wallet, so between the oyster and the reader there's a
layer of fabric, a donor card, and a layer of leather; i had been bringing
it up to the reader from above (so its approach vector was normal to the
plane of the reader), but i have now changed to sliding it on (so the
vector is parallel), and i no longer get the errors. It would seem that
the radio communication system is not very powerful.

It seems quite variable to me; one of our gates gives 70 and 94
constantly before it decides to open no matter how the card is placed.
The other six are far less temperamental.
--
Kat Me, Ambivalent? Well, yes and no.