Control apparatus for a xerographic type copying machine which enables the service technician to give the machine operator or user, as the operator's experience and training progresses, increased control over, and responsibility for, critical machine operating settings. The control apparatus includes a master lock to prevent unauthorized tampering with the machine settings by anyone except the authorized service technician. Individual locks, accessible only to the service technician, are provided for controls which it is expected that the operator or user, with training and experience, can ultimately handle. To nevertheless restrict and control the degree of operator responsibility and involvement in adjusting machine operating settings, means are provided with each control to enable the amount of adjustment that can be made limited.