G04C21/00—Producing acoustic time signals by electrical means
G04C21/16—Producing acoustic time signals by electrical means producing the signals at adjustable fixed times
G04C21/20—Producing acoustic time signals by electrical means producing the signals at adjustable fixed times by closing a contact to ring an electromechanical alarm
G04C21/22—Producing acoustic time signals by electrical means producing the signals at adjustable fixed times by closing a contact to ring an electromechanical alarm put into action by the arbor of a mechanical alarm work
ABC of the Telephone: A Practical and Useful Treatise for Students and Workers in Telephony, Giving a Review of the Development of the Industry to the Present Date, and Full Descriptions of Numerous Valuable Inventions and Appliances