A modular structure for safety switches for controlling access for machines and industrial plants, comprising: - a casing adapted to be anchored to a fixed part of the access to be controlled and housing thereinside switching means for controlling one or more control and/or service circuits of the machine or plant; - drive means adapted to interact with said switching means upon the opening/closing of the access for opening/closing of one or more circuits; - a set of controls ( 4 i -4 v) having functions different from each other; - an auxiliary module ( 3-3 v) adapted to be anchored to said casing and housing at least one control ( 4 i -4 v) of said set adapted to be manually operated to operate on said switching means and/or said drive means; wherein said auxiliary module ( 3-3 v) comprises a box hollow body having at least one opening for inserting at least one control ( 4 i -4 v) of said set, said opening being provided with first means for removably connecting said at least one control ( 4 i -4 v) of said set; characterised in that each of said controls ( 4 i -4 v) of said set is provided with a fastening rod ( 7 i -7 v) adapted to be inserted in said opening of said box body, the fastening rod ( 7 i -7 v) being provided with second connecting means complementary to said first connecting means for allowing the selective assembly of the respective control ( 4 i -4 v) of said set with said box body based on the designed function of said module ( 3-3 v); wherein said second connecting means are defined by counter-shaped portions ( 9 i -9 v) with respect to said first connection means whose external profiles are identical to each other for their selective anchoring to a same box body, wherein each fastening rod ( 7 i - 7 v) of each of the respective controls ( 4 i -4 v) also comprises a portion defined by a shape that differs from one another among respective controls ( 4 i - 4 v) of the set of controls ( 4 i - 4 v) to enable assembly of the auxiliary module housing one of the controls ( 4 i - 4 v) according to a function of the auxiliary module. - a casing adapted to be anchored to a fixed part of the access to be controlled and housing thereinside switching means for controlling one or more control and/or service circuits of the machine or plant; - drive means adapted to interact with said switching means upon the opening/closing of the access for opening/closing of one or more circuits; - a set of controls ( 4 i -4 v) having functions different from each other; - an auxiliary module ( 3-3 v) adapted to be anchored to said casing and housing at least one control ( 4 i -4 v) of said set adapted to be manually operated to operate on said switching means and/or said drive means; wherein said auxiliary module ( 3-3 v) comprises a box hollow body having at least one opening for inserting at least one control ( 4 i -4 v) of said set, said opening being provided with first means for removably connecting said at least one control ( 4 i -4 v) of said set; characterised in that each of said controls ( 4 i -4 v) of said set is provided with a fastening rod ( 7 i -7 v) adapted to be inserted in said opening of said box body, the fastening rod ( 7 i -7 v) being provided with second connecting means complementary to said first connecting means for allowing the selective assembly of the respective control ( 4 i -4 v) of said set with said box body based on the designed function of said module ( 3-3 v); wherein said second connecting means are defined by counter-shaped portions ( 9 i -9 v) with respect to said first connection means whose external profiles are identical to each other for their selective anchoring to a same box body, wherein each fastening rod ( 7 i - 7 v) of each of the respective controls ( 4 i -4 v) also comprises a portion defined by a shape that differs from one another among respective controls ( 4 i - 4 v) of the set of controls ( 4 i - 4 v) to enable assembly of the auxiliary module housing one of the controls ( 4 i - 4 v) according to a function of the auxiliary module.