Before revision: The electrical contact between the cup and the crystal had to be good, because it was important for this contact ' not to act as a second rectifying junction, creating two back-to-back diodes which would prevent the device from conducting at all.
After revision: The electrical contact between the cup and the crystal had to be good, because it was important for this contact not to act as a second rectifying junction, creating two back-to-back diodes which would prevent the device from conducting at all.