Teletypewriter line keyer with switching current regulator
AssigneeFrederick Electronics Corporation
InventorsJohn W. Spaniol, Ronald E. Tollum, Julius A. Barthelme
Life of this patent
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Abstract
A teletypewriter line keyer with a switching current regulator responsive to a floating, loop current powered voltage comparator used as a loop current monitor. The line keyer, which may have positive and negative line current keying, uses a single current monitor to control positive and negative current regulators responsive to the positive and negative keying respectively. The switching regulators operate within a relatively narrow band centered around the nominal signaling current, with filtering being provided for ripple control. The circuit may also include a keying detector and open loop detector for system monitoring.
Claims18
A switching network for selectively delivering an average current from either a negative power source or a positive power source to a load, comprising:
- (a) switching means responsive to input keying control signals for connecting one of the power sources to the load, the load current forming the loop current in a loop which includes the connected power source supplying the loop current, a portion of said switching means and the load;
- (b) a floating, loop current-sensing circuit responsive to the level of either a positive or a negative current in the load, for generating feedback control signals for operating said switching means to disconnect a connected power source from the load, the feedback control signals cooperating with the input keying control signals to control the connection and disconnection of a power source, said floating circuit developing its operating power voltages from the loop current itself;
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- (c) an energy storage circuit connected between said switching means and the load, for storing energy when either of the power sources is connected to the load, and for supplying stored energy to the load when the connected power source is disconnected.
A switching network for delivering an average current from either a negative power source or a positive power source to a load comprising:
- (a) first and second primary switches respectively responsive to first and second primary switch control signals for respectively connecting said positive and negative power sources selectively to the load, the load current forming the loop current in a loop which includes the connected power source, said primary switch connecting the connected power source and the load;
- (b) a floating, loop current-sensing means responsive to the current in said load, for generating control signals for operating said primary switches to disconnect the connected power sources when an upper level of load current higher than the average current level is sensed, and to enable reconnection of the disconnected power sources when a lower level of load current lower than the average current level is sensed, said current-sensing means developing its internal operating power voltages from the loop current itself;
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- (c) first and second energy storage circuits, respectively connected between said first and second primary switches and the load, each energy storage circuit storing energy when its associated power source is operatively connected to the load through its associated primary switch, and delivering the stored energy to the load when its associated power source is not so connected.
In a teletypewriter switching system, said switching system having,
- (i) a keyer for transmitting data as a predetermined current level in a load,
- (ii) a receiver for receiving data from said keyer, and
- (iii) a power source having both a positive and a negative power supply,
- the improvement in said switching system comprising an improvement in said keyer, comprising:
- (a) primary switch means responsive to the keying control signals for connecting a power supply to the load, said connected power supply delivering a predetermined loop current in said load, the load current forming the loop current in a loop including the connected power supply, said primary switch means connecting the connected power supply and the load;
- (b) floating, loop current-sensing means responsive to the load current for generating feedback control signals for operating said primary switch means to disconnect the operatively connected power supply from the load, said current-sensing means generating its own internal power supply requirements from the loop current irrespective of the polarity of the loop current;
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- (c) energy storage means connected between said primary switch means and the load, for storing energy when said primary switch means is operatively connecting a power supply to the load, and for delivering the stored energy to the load when the power supply is disconnected from the load.
Dependencies are inferred from the claim text.