Farthest advance circuit for a remote station dictating system

Claim 2

An improved record/playback system of the type having a plurality of remote dictating stations connected to at least one common terminal at a central record/playback unit, the remote dictating stations each including a separate privacy and seizure control circuit, the central record/playback unit having an endless loop of recording material, transducing head means for recording signals on and playing signals back from the recording material and electro-mechanical means for movably supporting the loop of recording material and advancing the loop of recording material past the transducing head means, wherein the improvement comprises first switch means for sensing the tautness of the loop of recording material prior to being advanced past the transducing head means, electronic second switch means connected between the first switch means, the privacy and seizure control circuits and the electro-mechanical means, first bias means for supplying a first voltage of a predetermined polarity through the first switch means to bias the second switch means into a conductive state when the first switch means is closed due to the slackness of the loop of recording material, a portion of the first voltage further passing through the conductive second switch means to activate the electro-mechanical means to advance the loop of recording material past the transducing head and to disable the seizure control circuits of the remote dictating stations.

Claim 3

An improved record/playback system as recited in claim 1 wherein each remote dictating station includes a control circuit and each privacy and seizure control circuit includes electronic third switch means connected in series between the control circuit and the common terminal, second means at the central record/playback unit for selectively supplying a second bias voltage of a polarity opposite to the first voltage to the third switch means to make it become substantially conductive, and electronic fourth switch means responsive to the conductive state of the third switch means and connected between the first bias means and the third switch means for supplying the first voltage to the third switch means to maintain it in its substantially conductive state when the third switch means is made substantially conductive by the second bias means.

Claim 4

An improved record/playback system as recited in claim 2 wherein the privacy and seizure control circuits each further include a first diode, a first, a second, and a third resistor and fifth switch means having two terminals, the third switch means includes a first transistor of one conductivity type including a collector electrode and an emitter electrode and having one of said collector and emitter electrodes connected to one terminal of the fifth switch means, its base electrode connected through the first resistor to the common terminal, and the other of its collector and emitter electrodes connected to one lead of the second resistor, the third resistor being connected between the base electrode of the first transistor and the one terminal of the fifth switch means, the first bias means includes a voltage source connected to the other lead of the second resistor, the fourth switch means includes a second transistor of a conductivity type opposite to that of the first transistor and including a collector electrode and an emitter electrode and having one of said collector and emitter electrodes connected to the base electrode of the first transistor, the other of its collector and emitter electrodes connected to the voltage source of the first bias means, and its base electrode connected to the one of the collector and emitter electrodes of the first transistor which is connected to the second resistor, the first diode being connected between the other terminal of the fifth switch means and the common terminal of the central record/playback unit with its polarity oriented such that current which passes through the first transistor and the fifth switch means is passed through the first diode to the common terminal, and the second bias means including a second bias voltage source which is connected to the other terminal of the fifth switch means.

Claim 5

An improved record/playback system as recited in claim 2 further comprising at the central record/playback unit electronic fifth switch means responsive to the flow of current from the first bias means through the third switch means and connected between the first bias means and the electro-mechanical means for supplying the first voltage to the electro-mechanical means when the third switch means is conductive and drawing current from the first bias means.

Claim 6

An improved record/playback system as recited in claim 4 wherein the electro-mechanical means includes motor driven means for advancing the loop of recording material, the motor driven means including a relay coil, electronic sixth switch means connected in series both between the first bias means and the relay coil and in series between the first bias means and the third switch means to supply the first voltage as a reverse bias voltage to the third switch means, the second switch means and the sixth switch means each having separate control electrodes connected together and in series with the fifth switch means to the first bias means, the Sixth switch means being made conductive and non-conductive in response to the conductive state of both the second and fifth switch means, and solenoid means for selectively engaging the loop of recording material with the motor driven means, and electronic seventh switch means for selectively completing a series connection between the first bias means, the solenoid means and the common terminal to energize the solenoid means, the second switch means being connected between the first bias means and the seventh switch means to provide a bias which makes the seventh switch means conductive when the second switch means becomes conductive.