Without both boxes connected to the same phone line you are breaking the T&C's.
SKY do monitor these installations and are not afraid to warn subscribers and then just charge you full price for both subscriptions if you fail to remedy the situation.
Using the same phone line is the best way open to SKY to confirm that both boxes are in the same location and not been sold or given to someone else, you are the victim of other peoples piracy in the years gone by
You could of couse put it a diy phone extension, although depending upon the cable run and the layout of your rooms that may not be practical.
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