Oct. 29, 1946.‘ - ' BJM. HARRISON - 2,410,065‘ ELECTRICAL CIRCUIT Filed Aug. 6. 1935 ' ) aeciewsn AMPLIFIER / HIGH é -_ i % QF'REQUEMQY ' ‘j; > GENEEWT'ORQ. ELECTRIC ' ‘ / l5 I INVENTOR. Ear/mm M Harrison ATTORN . , Patented Oct. 29, 1946 ZAMQS UNITED STATES PATENT OFFICE 2,410,065 ELECTRICAL CIRCUITS Bertram M. Harrison, Newton, Mass, assignor, by mesne assignments, to Submarine Signal Company, Boston, Mass, acorporation of Dela ware Application August 6, 1935, Serial N 0. 34,938 .6 Claims. » The present invention relates to a system for transmission and reception of compressional waves where the same unit serves both to project the. compressional wave energy and to pick up or receive the energy from the medium after re?ec tion from the object whose distance is being measured or whose position. is being observed. In systems of this nature it is usually necessary tohave the projecting'and receiving device, which is sometimes called a transceiver, connected to some form of amplifying circuit to amplify the impulses picked up by the projector when used as a pickup unit. Under these conditions if the ampli?er remains in circuit with the energizing (Cl. 177—386)» the echo of the transmitted signal and other sounds such as extraneous water noises. This applies also in the case of frequencies that may be present in the supply source itself so that the present system provides a remarkably quiet method of listening. 7 With all these advantages it will be noted from consideration of the speci?cation that practically the entire terminal voltage of the projector when used as a pickup unit is impressed across the re ceiving circuit so that practically one hundred percent e?iciency is maintained in the system when used for receiving. > The present arrangement will be more fully de 15 scribed and better understood from a considera ceiver is apt to be paralyzed or damaged by the tion of the description given below in connection power applied to the system. with the drawing which shows schematically the Various means have been tried to maintain the invention as applied to depth sounding and sound receiver ampli?er in circuit while the power is ranging. being applied and at the same time protect them 20 In the drawing I indicates the transceiver so that the full power of the source is not applied which. may be a high frequency oscillator of the to it. Various means and methods have been magnetostriction or piezo-electric means. The used for this purpose, some of which include oscillator is in a series circuit with the induct applying a protective discharge device across the ance L1, the capacity C1, which may be‘ variable, receiver ampli?er which breaks down when a large voltage is applied to the projector and 25 and the inductance L2. Shunted across‘ the in ductance L2 by the leads 3 and Q is a receiver am which again assumes; ahigh impedance when pli?er unit 5 which may be and preferably is a the applied voltage has been removed. In other vacuum tube ampli?er of the usual type. The systems relays have been used to shift the con nections from sending to receiving after the 30 output of the receiver ampli?er may be con nected by the line 95. and the ground ‘I to an indi sending impulse has been delivered. cating system 8. The indicating system is pref’ In these means and methods and in others erably of the continuous rotating. type in which that have been attempted various di?iculties still a shaft 9 is continually rotating, the shaft carry- ' seem to persist. Either the arrangement is not ing indicating disc I0 and the cam 20 for operat rapid enough to allow the receiving system to 35 ing the transceiver l as a projector. The indi be used soon enough after the impulse has been cating disc Ill may be provided with an indicating transmitted or too much energy is consumed device I I, as, for instance, a neon discharge tube either across the source when the system is used which is connected through to the line 6 through for receiving or across the receiver when the system is used for transmitting. In addition to 40 the commutator ring 12 and the brushv l3. The other side of the neon light may be grounded this, in some of the systems the receiver is not means operating the unit as a projector, the re sufficiently protected to prevent the receiving circuit from becoming paralyzed for ‘too long a time after the impulse has been emitted. In the present invention the receiving circuit ~ is at all times connected with the pickup unit and similarly the power supply and. the receiving system is at all times operable immediately after the emitted signal has been given. In addition to this, there is no possibility for the receiver to become paralyzed by the power in the driving or projection-energizing circuit. In this manner immediately after a short signal has been emitted, the system is capable of receiving the re?ected . echo and therefore very short distances can be = measured by the echo system employing the time-of-travel method. In addition to these advantages the coupling circuit may be tuned to the signal that is being as indicated at It. A scale I5 may be provided with an indicating device, and the cam 28 may be adjusted with ref erence to the position of the discharge tube on the scale so that thecontacts It and I‘! may emit a signal by operating the driver or high frequency electric generator IS, the output I9 of which is coupled to the inductance L1 as indicated. When the contacts I6 and I‘! are closed, thedriver or high frequency electric generator energizes the projector and an impulse is transmitted to the propagating medium which, after re?ection from the object whose distance and direction are being observed, returns to energize the transceiver again as a, pickup unit. This impulses impresses a potential across the inductance L2 which is con‘ nected to the input of the receiver ampli?er where it is ampli?ed and then impressed upon the discharge tube I I to produce an indication of received so that. a selection can be made between (ii) distance. By reading the position’ of the light 2,410,065 3 4 across said inductance, and said capacity and adjacent to the scale, the distance may be meas power source being tuned for series resonance at ured. In the system as described the impedances L1, L2 and C1 must be chosen with reference to the the frequency at which the system operates. 2. In a system for the transmission and re ception of compressional waves, a series circuit including a coil of substantially negligible re sistance adapted to have a high frequency cur rent impressed upon the coil, a compressional chosen so that at the frequency at which the wave transmitting and receiving device and sepa transceiver is operated, the reactive components rate capacities and inductances having substan of these two elements are equal and opposite so 10 tially negligible resistance, forming a series cir that the effective impedance in series is equal to cuit, the capacities and coil being balanced for their resistive component. the high frequency current impressed upon the The impedance of the inductance L2 is chosen coil, and an amplifying unit shunted across such at about one-tenth the value of the impedance inductances, the impedance of such inductances of L1, but it may be chosen at other values, de 15 being substantially less than the impedance of pending upon the amount of voltage allowable the transmitting and receiving device. across this inductance when the circuit is being ' 3. In a system for the transmission and re energized by the driver or high frequency electric ception of compressional Waves, a series circuit generator. In general the impedance value of including a transceiver, a coil of substantially L2 is kept somewhat below the value of the im negligible resistance adapted to have a high fre pedance of the transceiver, as under these con quency current impressed upon the coil, separate ditions the circuit appears to have its greatest inductance and capacity elements also having eihciencyj , Since L1 and C1 are tuned to reso substantially negligible resistance, and a receiv nance for the frequency that is being transmit ing ampli?er unit connected across said inductive ted,‘they will alsoibe in resonance for the fre element, such coil and condenser being tuned to quency at which the transceiver acts as a re resonance for the frequency at which the system ceiver so that the impedance across the trans is to operate, the impedance of said inductive ele ceiver under these conditions will be made up ment being substantially less than the impedance practically entirely by the impedance of the in of the transmitting and receiving device. ductance L2. Under transmitting conditions the 4. In a system for distance ?nding a series cir Voltage across L2 may be about 40% of the volt cuit including a coil of substantially negligible frequency and the impedance of the transceiver to bring about the desired operating conditions. In general the inductance L1 and capacity C1 are age across the transceiver, and under receiving resistance adapted to have a high frequency cur rent impressed upon the coil, a transmitting and receiving unit, means for receiving and indicating ' conditions the voltage across the inductance L2 may be substantially equal to that across, the transceiver. It is evident, therefore, that the re ceiver ampli?er is substantially protected from the full voltage of the driving unit, and these features together with the selective tuning of the impedance L2 across’ the receiver ampli?er are in strumental in providing an e?lciently operating 40 circuit. ’ ' ' When the system disclosed in the system is used for transmission, the circuit including L1, C1 and L2 and the projector l are so propor tioned that series resonance is established across LlCl which means that the full voltage of the ‘ receiving units, said receiving circuit including in series a capacity of negligible resistance and an inductance also of negligible resistance balanced at resonance with each other at the frequency impressed, and said receiving and indicating means being connected across said inductance, the impedance of said inductance being substan tially forty per cent of the impedance of the / transmitting and receiving device, 5. In a system for the transmission and re generator or driving unit is impressed in series across the projector and inductance L2. If, as stated above, the voltage across L2 may be 40% of the voltage across the receiver and there are ‘100 volts'impressed across the transceiver, then there would be 40 volts across the inductance L2 and therefore the receiver ampli?er does not bear the shock of the full voltage across the pro jector. When the system is used for reception of the signal which the projector has already sent out for which the system is primarily designed to be used, the receiver signal being tuned to series resonance for L1 and C1, the entire volt age appearing across the projector will be im pressed across the inductance L2. the impulse picked up by said transmitting and ' ' Having now described my invention, I claim: ception of compressional waves, a series circuit including a plurality of inductances, a capaci tance and an electromechanical energy inter changing device, the capacitive reactance and the inductive reactance of one of said inductances being substantially equal in magnitude at the frequency at which the said device is designed to operate and amplifying means connected in cir cuit with the remaining of the aforesaid induct ances ‘which is substantially less in magnitude than the inductance having a reactance substan tially equal to that of the capacitance reactance. 6. In a system for the transmission and recep tion of compressional waves, a series circuit in cluding therein, a transceiver, a receiver ampli?er input element, a coupling element through which 1. In a system for measuring distance, means for transmitting a short compressional wave im a high frequency power supply is furnished to the transceiver for transmitting and a capaci pulse, means for picking up said impulse after re?ection from the object whose distance is to be measured, said pickup and emitting means being series tuned to resonance for the transmit being the same, means comprising a series cir cuit including said pickup means, a power source for generating high frequency electric current, " capacity and inductance elements, said induct ance elements having an impedance substantially less than the transmitting and receiving device, and means for amplifying and indicating the re ceived impulse, said means being connected tance, the said coupling element and capacitance ting frequency whereby when the series circuit is operating as a transmitting circuit only a part of the impressed electromotive force will be im pressed on the amplifying'circuit, while when it is operating as a receiving circuit all of the elec tromotive force developed by the transceiver will be impressed upon the amplifying circuit. BERTRAM M. HARRISON.