United States Patent  [ii] Patent Number: 4,806,905
McGowan, III et al.  Date of Patent: Feb. 21,1989
 TRANSMITTER FOR TRANSMITTING ON A TWO-WIRE TRANSMITTING LINE
 Inventors: David L. McGowan, III, Warminster;
Steven M. Oxenberg, Richboro, both of Pa.
 Assignee: Honeywell Inc., Minneapolis, Minn.  Appl. No.: 914,031  Filed: Oct. 1,1986
 Int. CI.4 H04M 11/04; G08C 19/16
 U.S. a 340/310 R; 340/870.18;
340/870.39; 375/5; 375/24
 Field of Search 340/310 R, 310 A, 870.39,
340/870.40, 825.06, 870.16, 870.18; 375/5, 7,
 References Cited
U.S. PATENT DOCUMENTS
4,400,688 8/1983 Johnston et al 340/310 R
4,520,488 5/1985 Houvig et al 340/310 R
4,611,274 9/1986 Machino et al 340/310 R
Primary Examiner—John W. Caldwell, Sr.
Assistant Examiner—Tyrone Queen
Attorney, Agent, or Firm—Mitchell J. Halista; Albin
A transmitter for repeatedly transmitting a measured value in the form of a digital signal through a two-wire transmission line, includes a receiving unit for receiving a digital command signal from a communicator through the two-wire transmission line, and a processor for sending out a response signal in response to the command signal upon reception thereof. The measured value is sent using a newest measured value after repetitive transmission of the measured value is interrupted. The measured value is transmitted from the transmitter by a change in current supplied to the two-wire transmission line, and reception of the command signal is performed by a change in interline voltage of the twowire transmission line.
15 Claims, 8 Drawing Sheets