If I understand correctly, it is necessary to press d plus e plus f when changing batteries only if you think it will take longer than 30 seconds. I get everything ready, then make the change as quickly and smoothly as possible. Afterward, all I need to set is time and date. Lois -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.14.11/219 - Release Date: 1/2/2006