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Oct. 29, 1946.‘ -
' BJM. HARRISON
-
2,410,065‘
ELECTRICAL CIRCUIT
Filed Aug. 6. 1935
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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.
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