04656318 is referenced by 53 patents and cites 7 patents.

A modem which can detect an incoming call and provide an indication of the incoming call to a host computer while the power to the modem is turned off, comprising a switchable power supply that can be turned on and off by a remote input from the host computer, a ring detector circuit that monitors for incoming calls and notifies the host computer through an open drain output without using power from the computer, and isolator circuits that provide isolation on all the input/output lines between the modem and the computer to prevent power leakage from the computer's power source when the switchable power supply is turned off.

Title
Modem with power-off ring detection
Application Number
6/732525
Publication Number
4656318
Application Date
May 9, 1985
Publication Date
April 7, 1987
Inventor
Harold B Noyes
Corvallis
OR, US
Agent
James M Williams
Assignee
Hewlett Packard Company
CA, US
IPC
H04M 11/00
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