Abstract: In a digital copier of the type writing image data read by a scanner in a memory and transferring them from the memory to a printer, a memory change flag indicative of whether or not to calculate the occupancy of the memory is checked. If the flag is set, the occupancy of the memory is calculated and sent to a system controller. One or more reference amounts, which are easy for the user to grasp (e.g. amount corresponding to a single paper of A4 size), can be entered on an operation and display panel. The occupancy of the memory is displayed on the operation and display panel on the basis of each of the reference amounts. The memory change flag is set when image data have been fully written to the memory and when the discharge of a recording medium carrying an image thereon from the copier has been detected (end of read-out). The copier prevents the image data stored in the memory from being destroyed.

Abstract: A device installed in a copier, facsimile apparatus or similar image forming apparatus of the type including a fixing unit displays a waiting time necessary for the warm-up of the apparatus. The device calculates an elevation rate of fixing temperature within a predetermined time interval, produces a difference between a current temperature of the fixing unit and a set fixing temperature on the basis of the elevation rate, and thereby determines a waiting time. Further, the waiting time is determined on the basis of a temperature inside the apparatus when the ambient temperature is comparatively low and on the basis of a temperature of the fixing unit when it is higher than a predetermined level.

Abstract: A charge quenching apparatus for quenching unnecessary charges on a latent electrostatic-image bearing photoconductor of an electrophotographic copying machine for making copies with clean margins when the size of the maximum-latent-image area on the photoconductor, corresponding to the size of the original, is smaller than the transfer sheet employed, in the unit magnification and in the variable magnification, and for making copies without applying excess load to a cleaning apparatus of the photoconductor when copies bearing part of the image of the original are made or when copies bearing a reduced-size image of the original are made. In the charge quenching apparatus, the size of the maximum-latent-image area selected and the size of the transfer sheet selected are compared, and charges in the area outside the area corresponding to the smaller size determined by the above-mentioned comparison are quenched.