« PreviousContinue »
United States Patent D9]
[li] 4,314,103  Feb. 2,1982
 TELEPHONE ANSWERING SYSTEM WITH SIMULATED DIAL TONE DISCONNECT PROTECTION
 Inventor: Donald R. Wilson, Santa Cruz, Calif.
 Assignee: Plantronics, Inc., Santa Cruz, Calif.
 Appl. No.: 151,295
 Filed: May 19,1980
Related U.S. Application Data
 Division of Ser. No. 947,095, Sep. 29,1978, abandoned.
 Int. C1.3 H04M 1/65
 U.S. CI 179/6.11; 179/1 MN;
179/6.15; 179/6.18; 179/6.14
 Field of Search 179/6.07, 6.11, 6.15,
179/6.18, 6.20, 6.09, 6.17, 6.02, 1 MN, 5 R
 References Cited
U.S. PATENT DOCUMENTS
3,647,985 3/1972 Langendorf et al 179/6.09
3,715,518 2/1973 Campbell et al 179/6.11
3,725,589 4/1973 Golden 179/6.09
3,899,645 8/1975 Brafman 179/5 R
3,927,260 12/1975 Amundson et al 179/1 MN
3,978,289 8/1976 Konno 179/6.11
4,086,434 4/1978 Bocchi 179/5 R
4,150,255 4/1979 Theis et al 179/6.17
4,160,125 7/1979 Bower et al 179/6.02
Primary Examiner—Bernard Konick
Assistant Examiner—Donald McElheny, Jr.
Attorney, Agent, or Firm—Arnold, White & Durkee
An automatic telephone answering system wherein disconnection from the telephone line following calling party hang up is in response to the detection of dial tone, utilizes a signal detector responsive to voice and steady tone signals for providing an indication of the status of an incoming signal on the telephone line, and a processor for monitoring line signal status to determine the presence of dial tone. Following a determination of the presence of dial tone as an incoming line signal, the processor acts to automatically disconnect the system from the telephone line by opening a telephone line connection relay. The determination of dial tone is made based upon the continuous existence, over a predetermined time interval, of an incoming line signal status representative of a steady tone signal, rather than an absolute, single event detection. An automatic telephone answering and message recording system having remote access message playback, and which disconnects from the telephone line in response to dial tone, further includes processor actuated circuitry for inserting a blank interval in an incoming line signal prior to being recorded. The circuitry is actuated upon a determination by the processor that the incoming line signal is a steady tone signal, the determination being made based upon the existence, over a predetermined time interval, of an incoming line signal status representative of a steady tone signal. The duration of the time interval for such determination being a shorter period than the duration of the time interval for a dial tone determination.
1 Claim, 3 Drawing Figures