referring more particularly to fig1 there is shown a bilateral converter for converting between a high voltage v a at terminals 10 to a lower voltage v b at terminals 11 and comprising a transformer 12 having a turns ratio substantially proportional to the ratio between the two voltages v a and v b . a transistor 13 on the input or high voltage side of transformer 12 serves as a chopper operated by switching signals through resistor 14 and winding 15 of transformer 16 . a driver oscillator 17 of standard design is connected to primary winding 18 of transformer 16 to provide a switching signal at any desired frequency , but preferably at the frequency outside of the range of the intelligence signals which are to be operated upon by the electronic circuits to be powered from the converter of fig1 . in a telephone system , for example , oscillator 17 provides switching signals above the audio range and thus has no signal components which might interfere with the communications signals . diode 19 is provided in series with the output or low voltage side of transformer 12 and serves to rectify the voltages on this side of transformer 12 . the switching signal component of this rectified voltage is filtered out by capacitor 20 to provide at terminals 11 a voltage at the lower level v b . the value of voltage v b is given by the relation ## equ1 ## where n is the turns ratio of transformer 12 , t on ( 13 ) is the period for which transistor 13 is turned on and t off ( 13 ) is the period for which transistor 13 is turned off . the portion of the circuit of fig1 described above comprises a standard energy storage type dc - to - dc converter . transistor 13 operates between cutoff and saturation to deliver pulses of current to winding 21 of transformer 12 . these current pulses induce corresponding voltages in the secondary winding 22 of transformer 12 to build up a voltage across capacitor 20 . diode 19 rectifies this voltage while capacitor 20 filters out the switching transients . a battery 23 can be connected across terminals 11 and the voltage across capacitor 20 utilized to charge battery 23 . this charging action continues as long as the current can be drawn through the winding 21 from terminals 10 . this current flow is supplied from a power source connected to terminals 10 such as a central office battery at the other end of a telephone pair . if a direct current load is connected across terminals 10 , it tends to draw current through winding 21 . transistor 13 is thereby reverse - biased and remains cut off despite the signals to its base . under this condition , however , transistor 24 , in series with winding 22 of transformer 12 becomes operative and , by means of a switching signal from resistor 25 and winding 26 of transformer 16 , is operated between cutoff and saturation . this switching action causes pulses of current to flow through winding 22 and introduces corresponding but higher voltage pulses in winding 21 . these pulses are rectified by diode 27 and deposit a charge on capacitor 28 . under these conditions , current can be delivered to the load connected to terminals 10 and energy is transferred from battery 23 to this load . diode 19 remains reversed biased in this mode and is not operative in the circuit . the value of the voltage v a is given by the relation ## equ2 ## where n is the turns ratio of transformer 12 , t on ( 24 ) is the period for which transistor 24 is turned on and t off ( 24 ) is the period for which transistor 24 is turned off . by operating transistors 13 and 24 from the source 17 but with opposite phases it can be seen that the bilateral converter of fig1 operates automatically to convert energy from the high to the low voltage level or from the low to the high voltage level in response to the load presented at terminals 10 . if a telephone line is connected to terminals 10 , a load can be placed anywhere along the telephone line and still be supplied from battery 23 . on the other hand , a low voltage load can be placed across terminals 11 and be supplied from battery 23 in accordance with well - known and conventional practice . the bilateral converter of fig1 can therefore be used in the same manner as a conventional converter to supply low voltage loads at a single remote location and at the same time can be used to supply high voltage loads at any point along the transmission line . the bilateral converter of fig1 is of the so - called &# 34 ; energy storage &# 34 ; type in which the reactance of transformer 12 serves as a storage mechanism for energy between current pulses . this form of converter is illustrated in fig1 only because of the relative simplicity of this type of converter from a circuit viewpoint . the principles of the present invention can just as readily be applied to other types of dc - to - dc converters in a straightforward fashion . it is only necessary to insure that the circuit arrangements are complementary on both sides of the converter and that the turns ratio or other voltage converting mechanism accommodates an appropriate ac voltage level conversion . another bilateral converter using the so - called switching type dc - to - dc conversion is illustrated in fig2 . referring more particularly to fig2 there is shown a bilateral converter including transformer 112 having a center - tapped high voltage winding 121 and a center - tapped low voltage winding 122 . a pair of switching transistors 113 and 113 &# 39 ; are connected in a push - pull configuration with their collector electrodes connected to opposite ends of winding 121 . high frequency switching signals are coupled from center - tapped winding 115 of transformer 116 through resistors 114 and 114 &# 39 ; to the respective bases of transistors 113 and 113 &# 39 ;. high frequency pulses from driver oscillator 117 are supplied to winding 118 of transformer 116 to drive transistors 113 and 113 &# 39 ; alternately into cutoff and into saturation . due to the center - tapped arrangements , transistors 113 and 113 &# 39 ; are turned on alternately , one being on while the other is cut off . current is delivered from the upper one of terminals 110 through the center tap of winding 121 and alternately through transistors 113 and 113 &# 39 ; to the lower one of terminals 110 . these current pulses through winding 121 induce voltages across winding 122 at a lower voltage level ( due to the turns ratio ) which are rectified by diodes 119 and 119 &# 39 ;, respectively , and delivered as a dc voltage to terminals 111 . capacitor 120 serves to filter out the switching components in this voltage . as before , a battery 123 can be connected across terminals 111 to be charged by the voltage supplied at terminals 110 . the voltage relationships are the same as shown in equations ( 1 ) and ( 2 ). a direct circuit load placed across terminals 110 draws current through winding 121 in such a direction as to cut off transistors 113 and 113 &# 39 ;. currents induced in winding 122 permit transistors 124 and 124 &# 39 ; to be turned on by signals through resistors 125 and 125 &# 39 ; and winding 126 of transformer 116 . pulses of current are delivered from battery 123 through winding 122 . the voltage thereby induced in winding 121 is rectified by diodes 127 and 127 &# 39 ; to provide a voltage across capacitor 128 . capacitor 108 filters out the switching frequencies . as before , low voltage loads can be placed across terminals 111 to be powered from battery 123 or , in the absence of battery 123 , from remotely supplied energy at terminals 110 . on the other hand , high voltage loads connected across terminals 110 can also be supplied from battery 123 . the bilateral converters of fig1 or 2 are merely illustrative of the type of circuits in accordance with the present invention that serve to bilaterally convert direct current energy between two voltage levels . other types of dc - to - dc converters can be modified in a similar manner in accordance with the teachings of this invention to provide the same result , as will be seen in the remainder of the figures . moreover , standard voltage regulation techniques can be used to maintain the output voltage at precisely controlled values . it should be noted that , from the viewpoint of terminals 110 , the circuits of fig1 and 2 both appear to be batteries having terminal voltages at the higher voltage level . these &# 34 ; electronic batteries &# 34 ; operate much like conventional batteries in that they can be used to power high voltage loads and they can be charged from conventional charging sources . on the other hand , only relatively inexpensive electronic components and an inexpensive low voltage battery are required to realize these bilateral converters . these high voltage electronic batteries can therefore be realized at lower cost than a conventional high voltage battery . driver oscillators 17 and 117 may be inexpensive circuits since the frequency value is relatively unimportant and since frequency stability is not critical . this oscillator may be realized in integrated circuit form to further reduce the cost and size of the bilateral converter . as previously noted , more standard configurations of dc - to - dc converters can be made bilateral simply by arranging the input and output halves of the converter to be symmetrical , or at least complementary . the balance of the figures in the drawings disclose some of the possible arrangements of bilateral dc - to - dc converters embodying the principles of the present invention . in fig3 and 4 there are shown what might be called basic chopper circuits 50 and 51 . these chopper circuits form basic subunits of the bilateral converters to be described in connection with fig5 through 16 . basic chopper circuit 50 in fig3 comprises a n - p - n transistor 52 having its base electrode connected through resistor 53 and transformer 54 to a source 55 of driving pulses to switch transistor 52 between saturation and cutoff . a diode 56 is connected across and poled oppositely to the collector - emitter path of transistor 52 . the chopper circuit of fig3 operates to interrupt direct current flow between the upper lead 57 and the lower lead 58 under the control of driver oscillator 55 . the circuit of fig3 also operates as a rectifier for direct currents flowing in a direction from lead 58 to lead 57 by virtue of diode 56 . the basic chopper circuit of fig4 is identical to that of fig3 except that transistor 52 &# 39 ; is a p - n - p transistor and hence the voltage relationships and the polarity of diode 56 &# 39 ; have been reversed . the basic chopper circuits of fig3 and 4 can be used interchangeably in the circuit configurations of fig5 through 16 . it is necessary , of course , to insure that the basic chopper circuits ( bcc &# 39 ; s ) are poled correctly . it is also necessary that the transistor switches 52 and 52 &# 39 ; be turned on during appropriate halves of the switching cycle . these switching sequences will be apparent from the descriptions of fig5 through 16 and are easily obtained by driving all of the chopper circuits by the same driving oscillator . in the circuits of fig5 through 16 , the filter capacitors at the input and output terminals have been omitted for simplicity . it is clear that these could in fact , be omitted in some applications where voltage regulation is not important , or could be replaced with complex regulators as required by the expected loads . in fig5 then there is shown a block diagram of an energy storage type bilateral converter using basic chopper circuits 60 and 61 as the series arms of a t - network having inductor 62 as the shunt arm . for energy flow from left to right , circuit 60 supplies energy to inductor 62 on one - half cycle and direct current energy is delivered to the output terminals at v a through basic chopper circuit 61 on the negative half of the cycle . the ratio v a to v b is given simply by the ratio of the on times of the transistors in circuits 60 and 61 . in fig6 there is shown another t - network bilateral converter in which the shunt arm comprises a basic chopper circuit 63 . the circuit operates similarly to that of fig5 except that the shunt switching occurs rather than series switching to provide a return path for current on alternate half cycles . in fig7 yet another form of t - network bilateral converter is shown . in fig7 the inductor 64 is connected to basic chopper circuit 65 in an autotransformer connection to permit autotransformer action to assist in the voltage level conversion . in fig8 there is shown a simple single - ended transformer coupled bilateral converter corresponding directly to the converter of fig1 . similarly , in fig9 there is shown a push - pull type of bilateral converter corresponding to the converter of fig2 of the drawings . these are shown again here simply for purposes of comparison . other transformer - coupled converter configurations are shown in fig1 through 16 . fig1 the bilateral converter takes the form of half - bridge circuits in which basic chopper circuits 70 and 71 form adjacent arms of a bridge , the opposite arms of which are formed by capacitors 72 and 73 . a similar half - bridge configuration is provided connected to the other winding of transformer 74 to provide bilateral capability . in fig1 there is shown a full - bridge bilateral converter in which basic chopper circuits form all four arms of the bridge circuit on both the input and output windings of transformer 75 . in fig1 there is shown a double - ended transformer coupled bilateral converter similar to the converter of fig8 but including basic chopper circuits at both ends of the transformer windings . diodes 80 , 81 , 82 , and 83 are provided to complete full - bridges on each side of the transformer and thus permit full wave rectification . all of the bilateral conversion configurations described in connection with fig9 through 12 involve symmetrical circuit elements on both sides of the isolating transformer . such symmetry is not required for the proper operation of the circuits as can be seen in connection with the circuit configurations of fig1 through 16 . fig1 , for example , shows a bilateral conversion circuit having a half - bridge chopper configuration on the left - hand side of transformer 90 and a push - pull configuration on the right - hand side of transformer 90 . similarly , fig1 shows a bilateral converter having half - bridge configuration on the left - hand side of transformer 91 and a full - bridge configuration on the right - hand side of transformer 91 . fig1 shows a bilateral converter having a push - pull configuration on the left - hand side of transformer 92 and a full - bridge configuration on the right - hand side of the configuration . finally , fig1 shows a bilateral converter with a double - ended configuration on the left - hand side of the transformer 93 and a single - ended configuration on the right - hand side . it will be apparent that many other combinations of the various configurations will be as equally suitable as bilateral converters . it will be necessary in each case to arrange the switching phase for the various transistors to afford appropriate current paths for each direction of current flow . these are obvious from inspection of the drawings and thus have been described in detail only in connection with fig1 and 2 . it will be noted that the basic chopper circuits of fig3 and 4 are merely one type of current switching arrangements which are polarity sensitive and which can be bridged by oppositely poled unidirectional conducting devices . such circuit operation can also be obtained from configurations of silicon controlled rectifiers , motor and mechanical controls , and any other polarity sensitive switching arrangements . such other configurations will be readily apparent to those skilled in the art from the above description and are believed to clearly fall within the spirit and scope of the present invention .