Here's a description of the B-763 control column operation with one side jammed from page 12 of the MS990 NTSB accident report:
The captains and first officers control columns have authority to command full travel of the elevators under most flight conditions and normally work together as one system. However, the two sides of the system can be commanded independently because of override mechanisms at the control columns and aft quadrant. Therefore, if one side of the system becomes immobilized, control column inputs on the operational side can cause full travel of the nonfailed elevator. In addition, in many cases, control column inputs on the operational side can also result in nearly full travel of the elevator on the failed side through the override mechanisms. The elevator PCAs are installed with compressible links located between each bellcrank assembly and PCA input control rod to provide a means of isolating a jammed PCA, thus allowing the pilots to retain control of that elevator surface through its two remaining (unjammed) PCAs
https://www.ntsb.gov/investigations/...ts/AAB0201.pdf