Connecting UPS to power strip

[Anonymous user]

Hi I am using APC BX600C. Got a monitor, mac mini and a wifi router connected to it and had been using for 2years without any issues. I looking to connect an external monitor but got only one wall socket, so I tried connecting a extension board Bull-Socket-Switch-Extension-Board without surge protection to the wall socket and then the ups input and the external monitor to the output sockets of the extension board. But when i turned on the ups i got a long continuous red beep, was really afraid and turned it off, tried unplugging and connecting it again and it seems to be running without any issues now. Is it safe to keep it running or should i revert back to connecting my ups to the wall socket and if it is the latter is there any other possibility for connecting a extra monitor with a single wall outlet. I read about dangers of connecting ups to surge protectors Surge Protector to UPS but would it be okay for a power strip without any surge protectors