[Jim Wilks]

Originally Posted by Radical Pi

Been doing some math on this one, and I'm seeing enough electronics for 21 fields, not 19. It's the only way I can get the numbers on the more expensive electronics to come out evenly.

Standard practice with this sort of equipment is to buy spares. Often 10% is the figure used. In the case of 19 fields, that's enough for 2 more fields. Nobody wants a critical system down waiting for delivery of a replacement part.