of the tilt rod 39 is explained as shown in fig6 the tilt rod 39 to which the axle bush 37 is coupled is a member of the frequency modulation mechanism 2 of the blind adapted to control the tilting angle of the blind slats during frequency modulation the follower member 36 and the locating ring 38 are respectively stopped against the corresponding pawl 31 or 33 and the housing 10 and prohibited from rotary motion at an early stage however the tilt rod 39 and the axle bush 37 are continuously rotated to tilt the blind slats of the blind in the aforesaid example the frequency modulation mechanism 2 drives the tilt rod 39 alternatively a switching mechanism 200 may be used and coupled between the blind lift rod control lock 100 and the frequency modulation mechanism 2 the switching mechanism 200 comprises a coupling device 201 coupled to the tilt rod 39 a left lift cord 202 and a right lift cord 203 the lift cords 202 and 203 each have one end fixedly connected to the coupling deice 201 and the other end suspending outside the headrail of the blind the user can pull the left lift cord 202 to rotate the tilt rod 39 clockwise or pull the right lift cord 203 to rotate the tilt rod 39 counter clockwise when pulling the left lift cord 202 or the right lift cord 203 the follower member 36 and the locating ring 38 are simultaneously rotated with the tilt rod 39 and the axle bush 37 clockwise or counter clockwise alternatively the tilt rod 39 can be made independent of the frequency modulation mechanism 2 enabling the switching mechanism 200 to control the direction of rotation of.