discussed with reference to fig1 and 14 initially it will be noted that the structure of the first linkage subassembly 407 and of the second linkage subassembly 409 and the placement of the first transporter representation members 326 328 and of the second transporter representation members 330 332 will establish a fixed relationship between relative pivotations of the first terminal links 306 308 and of the second terminal links 310 312 at such times that the ternary links 236 238 are pivoted while the transporter representation members 326 332 remain in place and relative pivotations of the first transporter representation members 326 328 and of the second transporter representation members 330 332 at such times that the ternary links 236 238 are pivoted while the terminal links 306 312 remain in the reference positions thereof on the transporter representation members 326 332 that is a fixed relationship exists between the relative magnitudes of the angles 420 422 in fig1 and the relative magnitudes of the angles which have been designated 428 and 430 in fig1 the same symmetry considerations that require the identity of the angles of pivotation of the first terminal link 306 and second terminal link 312 and require the identity of the angles of pivotation of first terminal link 308 and second terminal link 310 in fig1 also require the identity of the angles of pivotation of first transporter.