Systemd-boot load another entry if main entry damaged

I use systemd-boot, I have two Linux systems, identical, two so that when updating the device, one is a backup And I don't understand, I have two systems, both are visible in the menu, by default, system #1 is loaded. Timeout 0. But if you delete this system manually, i.e. simulate a situation when the system is damaged and should start backup system #2, but there is an attempt to load the main one, there is a system boot error, and the backup one does not load. Only if you enter the boot menu and select it. How can I make it so that the backup one loads automatically? Is this possible? Is this called a fallback? All system have entries, all system visible in menu and can loaded. I expect that if system #1 is damaged, then system #2 should start But maybe I don't understand bootloaders correctly. I need in that, becouse device have not keyboard to choose system #2 by hands. So What should I do to automatically boot the backup system if the primary system is dead?