Question: How many frequencies have a line of east london and destination of crystal palace?
SQL: SELECT COUNT("Frequency (per hour)") FROM "2-1569516-1" WHERE "Line" = 'east london' AND "Destination" = 'crystal palace';

Question: Which line has an operator of the London Overground and ends at the Crystal Palace?
SQL: SELECT "Line" FROM "2-1569516-1" WHERE "Operator" = 'London Overground' AND "Destination" = 'Crystal Palace';