Are you looking to run a command based on whether or not the player is standing at that location, or just looking to activate a redstone comparator as your output?
If you're seeking comparator output, you can use
/execute if entity @a[x=insert_x_coord_here,y=insert_y_coord_here,z=insert_z_coord_here,distance=..1]
This will power a comparator if a player is standing 1 block or less from the position you want to test.
If you want to repeatedly run a command upon testing condition success,
/execute as @a[x=insert_x_coord_here,y=insert_y_coord_here,z=insert_z_coord_here,distance=..1] at @s run say I'm in location!
This will repeatedly spam "I'm in location!" if your within 1 block of the position you want to test. at @s will cause the command to be executed at the player's location, so not needed for the say command, but may very well be needed for some others. The command to be executed is always after run.
distance is a range defined as min..max, so if you want to test for a larger radius, you can increase max. increasing min will test for players at least _ meters from position. leaving out min or max will cause the corresponding ends of the range to become infinite.