Refers to a device that initiates an explosive, such as in bombs, shells, or fireworks. Technical term.
爆弾の信管が作動した。
The bomb's fuse activated.
時限信管をセットする。
Set the time fuse.
time fuse
time fuze; time fuse; time detonator
impact fuze; contact fuze; percussion fuze; direct-action fuze
proximity fuze; influence fuze; VT fuze
Compound of 信 (signal, trust) and 管 (tube, pipe), referring to a tube-like device that receives a signal to detonate. The exact historical derivation is uncertain.