Calling and warning apparatus for communication systems
United States Patent 2489202

Inventors:
Herbert, Selinger
Publication Date:
11/22/1949
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Assignee:
HARTFORD NAT BANK & TRUST COMP
Primary Class:
379/33
Other Classes:
379/375.010, 340/825.360, 331/59, 340/384.700, 331/64, 379/167.010
International Classes:
H04M9/00
US Patent References:
2376367Field telephone system