Dial-in data transmission system with standby capability
First Claim
1. Apparatus coupling a telephone data set at a first location to a telephone transmission line connected to a telephone instrument and for enabling communication of data between the data set and a second location over the telephone transmission line comprising:
- first switching means coupling said telephone instrument and said data set to said telephone transmission line in a first state of the first switching means;
clock means coupled to said data set through said first switching means in the first state of said switching means and for providing a trigger signal to said data set to cause said data set to communicate data over said telephone transmission line to the second location periodically at a predetermined time, and further for placing said switching means into a second state periodically during a predetermined time interval;
data transmission means coupled to said telephone transmission line and further coupled to said telephone instrument and said data set through said first switching means, and having a data set line connected to said data set through said switching means when said switching means is in said second state, said data transmission means normally connecting said data set line to said telephone transmission line, said data transmission means further having a telephone instrument line connected to said telephone instrument through said switching means when said switching means is in said second state, said data transmission means disconnecting said data set line from said telephone transmission line and connecting said telephone instrument line to said telephone transmission line in response to any of selected ones of a plurality of first electrical signals transmitted on said telephone transmission line, said first signals each being indicative of a call from a caller on said telephone transmission line, the data transmission means preventing disconnection of said data set in response to a selected one of the first signals, said data transmission means further comprising means for detecting any of said first electrical signals transmitted on said telephone transmission line without answering the call and for generating a second electrical signal when any of the first electrical signals on said telephone transmission line has terminated, indicating that the caller has hung up, said data set being adapted to communicate data to the second location via said first switching means over said data set line when said switching means is in said second state during said predetermined time interval and further via said data transmission means; and
the telephone transmission line in response to the generation of said second electrical signal after said selected one of said first electrical signals has terminated.
1 Assignment
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Accused Products
Abstract
A data transmission system causes a remote data set to dial a central computer periodically and also causes the data set to stand by at more frequent intervals to detect a call from, and then return a call to, the computer via a non-dedicated telephone line. The system is coupled to a telephone instrument, a data set, and the telephone transmission line and normally connects the telephone instrument and the data set to the telephone transmission line. A clock in the system triggers the data set to call the central computer periodically, as for example once a month. More frequently, as for example during one hour each night, the clock connects the telephone instrument and the data set to a subsystem which stands by during the interval to detect a possible call from the computer. During the interval, the telephone instrument is normally disconnected from the telephone transmission line and the data set remains connected by the subsystem. A counting circuit senses the number of ring bursts in a ringing signal from a caller and the central computer, if it needs to access the data set, is programmed to ring once and "hang up". When only one ring burst is sensed, the data set dials up the central computer. If more than one ring burst occurs, a non-computer call is being sensed and the data set is disconnected and the telephone connected to the telephone transmission line so that normal telephone usage is allowed.
73 Citations
26 Claims
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1. Apparatus coupling a telephone data set at a first location to a telephone transmission line connected to a telephone instrument and for enabling communication of data between the data set and a second location over the telephone transmission line comprising:
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first switching means coupling said telephone instrument and said data set to said telephone transmission line in a first state of the first switching means; clock means coupled to said data set through said first switching means in the first state of said switching means and for providing a trigger signal to said data set to cause said data set to communicate data over said telephone transmission line to the second location periodically at a predetermined time, and further for placing said switching means into a second state periodically during a predetermined time interval; data transmission means coupled to said telephone transmission line and further coupled to said telephone instrument and said data set through said first switching means, and having a data set line connected to said data set through said switching means when said switching means is in said second state, said data transmission means normally connecting said data set line to said telephone transmission line, said data transmission means further having a telephone instrument line connected to said telephone instrument through said switching means when said switching means is in said second state, said data transmission means disconnecting said data set line from said telephone transmission line and connecting said telephone instrument line to said telephone transmission line in response to any of selected ones of a plurality of first electrical signals transmitted on said telephone transmission line, said first signals each being indicative of a call from a caller on said telephone transmission line, the data transmission means preventing disconnection of said data set in response to a selected one of the first signals, said data transmission means further comprising means for detecting any of said first electrical signals transmitted on said telephone transmission line without answering the call and for generating a second electrical signal when any of the first electrical signals on said telephone transmission line has terminated, indicating that the caller has hung up, said data set being adapted to communicate data to the second location via said first switching means over said data set line when said switching means is in said second state during said predetermined time interval and further via said data transmission means; and
the telephone transmission line in response to the generation of said second electrical signal after said selected one of said first electrical signals has terminated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification