All signals herein required given by hand and arm shall be given from the left side of the vehicle in the following manner and such signals shall indicate as follows:
(A) Left turn. Hand and arm extended horizontally;
(B) Right turn. Hand and arm extended upward; and
(C) Stop or decrease speed. Hand and arm extended downward with palm to the rear.
(47 O.S. § 11-606) (`83 Code, § 15-908) Penalty, see § 71.999