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Mine Pager to Public Telephone Interconnect System.

Authors
Parkinson-HE
Source
MISSING :14 pages
Link
NIOSHTIC No.
10001357
Abstract
The mine pager phone to public telephone interconnect system permits mine paging telephones to be interconnected with the public phone system, thereby providing emergency and off-hours communications. The system, a push-to-talk, push-to-listen system, is compatible with any mine paging system utilizing DC voltage on the line to enable paging. A tone generator of the proper frequency enables an outside caller to page over mine pager system loudspeakers. A caller inside the mine can make an outgoing call to a preselected, preprogramed number with the use of a proper frequency tone generator. The system includes an automatic hangup timer that restricts the time off-line due to a wrong number or incorrect hangup to 20 seconds and 6 minutes, respectively.
Publication Date
19740101
Document Type
IH; Report of Investigations
Fiscal Year
1974
NTIS Accession No.
NTIS Price
Identifying No.
RI 7976
NIOSH Division
PRC;
Source Name
MISSING
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