Ngokweemfuno zomgangatho omtsha wesizwe wokuhanjiswa kokukhanya, izibonisi zinokukhetha ukuba zihambelane okanye zingahlangani neemfuno ezininzi;I-decibel buzzer ye-ceramic ephezulu kunye ne-chip yomqhubi ezinikeleyo isetyenziselwa ukuvelisa okuzinzileyo kunye nomgangatho wesandi okholekileyo;Insimbi engenasici okanye isibiyeli esitshizwe ngeplastiki asiyi kugqwala iminyaka emi-3.