DIFF Subgroup
G04C 21/28 by closing a contact to put into action electro-acoustic means, e.g. awakening by music
Introduced: September 1968
Full Title
Producing acoustic time signals by electrical means > producing the signals at adjustable fixed times > by closing a contact to put into action electro-acoustic means, e.g. awakening by music
No child classifications to compare. This is a leaf node in both IPC and CPC.