Abstract: In an electronic apparatus, a case houses an electronic apparatus main body and is electrically conductive. A terminal block is attached to a case wall of the case. In the terminal block, a main body portion is composed of an insulating material. An external terminal is inserted into a through-hole formed in the case wall, and is connected to the electronic apparatus main body. A capacitor is disposed inside the main body portion. An elastic member is disposed inside the main body portion, is composed of a conductive material, is interposed at least one of between the capacitor and the external terminal, and between the capacitor and the case wall, and fixes the capacitor inside the main body portion by pressing the capacitor. The capacitor and the elastic member configure a filter circuit that allows a noise current included in the external terminal to flow to the case wall.

Abstract: An inductor capacitor (LC) tank includes a first inductor and a first tunable capacitive array. The first inductor has a first terminal and a second terminal, and the first tunable capacitive array has a first terminal and a second terminal. The first tunable capacitive array is at a path branching from a first point between the first terminal and the second terminal of the first inductor, the first terminal of the first tunable capacitive array is coupled to the first point, and the second terminal of the first tunable capacitive array and the second terminal of the first inductor are coupled to a reference voltage.

Abstract: Various arrangements for mitigating voltage droop in a direct current circuit configured to power multiple capacitive loads are presented. A voltage source configured to output a direct current voltage to power the multiple capacitive loads may be present. First and second outputs electrically coupled with the voltage source such that the outputs, when electrically coupled with capacitive loads, provide a voltage to the capacitive load may be provided. A transformer module (which may include a transformer and an impedance) electrically coupled with the first output and the second output may also be provided. When the first capacitive load is electrically coupled with the first output, the transformer may be configured to mitigate droop of the first voltage to the first output upon the second capacitive load being connected to the second output and receiving inrush current.

Abstract: A power filter is provided, including a circuit board module, an insulating base, several connect terminals, and an inductor. The circuit board module includes a circuit board and several electronic components, wherein the circuit board forms several connect holes thereon and the electronic components are electrically connected to the circuit board. The connect terminals are fixed on the insulating base and each has a connecting part and a clamping part, wherein the connecting parts are joined with the connect holes of the circuit board. The inductor includes at least one wire with both terminals clamped by the clamping parts, and the wire is electrically connected to the circuit board module through the connecting parts.

Abstract: In a filter component with improved attenuation characteristics for common mode noise, an LC series resonance circuit disposed in each of a plurality of shunt circuits is connected at a first end to a first line and is grounded at a second end. The LC series resonance circuit disposed in each of the shunt circuits is grounded at a first end and is connected at a second end to a second line. With this configuration, the LC series resonance circuits resonate reliably so as to define attenuation poles. Accordingly, the resonant frequency of each of the LC series resonance circuits is set to be a frequency that effectively attenuates common mode noise.

Abstract: A winged coil structure and a method of manufacturing the same are disclosed. The winged coil structure includes an upper flexible plate, at least one upper magnetic induction coil, at least one upper connection pad, a lower flexible plate, at least one lower magnetic induction coil, at least one lower connection pad, at least one gold finger, a dielectric layer and at least one connection plug. The connection plug connects the upper connection pad and the lower connection pad through thermal pressing such that the gold finger, the upper magnetic induction coil, the upper connection pad, the lower connection pad, the connection plug, the lower connection pad and the lower magnetic induction coil are electrically connected. The upper flexible plate is provided with notched lines to be easily bent without damage to the upper and lower magnetic induction coils. Thus, a bendable feature for magnetic induction coils is provided.

Abstract: An inductor has a substrate and at least one coil of carbon nanotubes. A trench is formed in the substrate, and the carbon nanotubes are grown in the trench in order to form a coil for the inductor. In some embodiments, multiple coils may be formed in the trench as may be desired.

Abstract: The branch portion includes: a first circuit portion electrically connected to the main wire while extending to a leading end from a base end of the branch portion; a second circuit portion electrically connected to the main wire while extending to the leading end from the base end of the branch portion and electrically connected to the first circuit portion at the leading end of the branch portion; and a ground conductor that is disposed between the first circuit portion and the second circuit portion while extending to the leading end from the base end of the branch portion and has one end to be grounded and the other end to be opened.

Abstract: A coil has multiple coil sections connected to each other and each coil section includes a body portion and at least one direct or protrusive connecting portion disposed at one end of the body portion. Coil sections form at least one spiral path around the central axis of the coil, and on the projection of the coil along the central axis. The protrusive connecting portions protrude out of the path location of the direct connecting portions. Two connected coil sections form only one overlapped surface at the coupled parts of the direct or protrusive connecting portions. Regarding to the body portions in the same spiral path, a first end of one body portion is indirectly connected and disposed adjacent to a second end of another body portion. The second end has one surface with a virtual extension reaching the first end.

Abstract: A transmission circuit including four transmission component sets for Ethernet is provided. For each of the transmission component sets, a first capacitor and a first inductor are cascaded, the first inductor is coupled to the Ethernet connector via the first transmission line (TL), the first capacitor is coupled to the Ethernet chip via the second TL; a second capacitor and a second inductor are cascaded, the second inductor is coupled to the Ethernet connector via the third TL, the second capacitor is coupled to the Ethernet chip via the fourth TL; a first component set is coupled between a first contact and a second contact, the first contact is located between the first capacitor and the first inductor, and the second contact is located between the second capacitor and the second inductor; and a second component set is coupled between the second TL and the fourth TL.

Abstract: Provided is a noise reduction device including: a conductive bar of conductive material; a metal tubular portion with a through hole having the conductive bar penetrating therethrough and accommodating a magnetic material core and a substrate therein; a capacitor mounted on the substrate and having a first terminal connected to the conductive bar and a second terminal connected to an inner wall of the through hole; and a blocking unit blocking an opening of the through hole so as to affix the conductive bar with respect to the metal housing and the tubular portion. The tubular portion includes an outer peripheral surface having a threaded engagement part threadedly engaged with the metal housing; and the conductive bar has an outer end that functions as an output terminal.

Abstract: Provided is a noise reduction device including: a conductive bar of conductive material extending through a through hole in a metal housing to the outside; a magnetic material core of magnetic material disposed at a peripheral edge of the conductive bar; a substrate attached to the conductive bar so as to be adjacent to the magnetic material core; a capacitor mounted on the substrate and having a first terminal connected to the conductive bar and a second terminal connected to an inner wall of the through hole; and a blocking unit blocking an opening of the through hole so as to affix the conductive bar to the metal housing. The magnetic material core, the substrate, and the capacitor are disposed in the through hole blocked by the blocking unit; and the conductive bar has an outer end that functions as an output terminal.

Abstract: A composite electronic component may include: a composite body including a capacitor and an inductor coupled to each other, the capacitor having a ceramic body in which dielectric layers and internal electrodes facing each other with the dielectric layers interposed therebetween are stacked, and the inductor having a magnetic body in which magnetic layers having conductive patterns are stacked; an input terminal disposed on a first end surface of the composite body; an output terminal including a first output terminal disposed on a second end surface of the composite body and a second output terminal disposed on any one or more of upper and lower surfaces and a second side surface of the capacitor; and a ground terminal disposed on any one or more of the upper and lower surfaces and a first side surface of the capacitor and connected to the internal electrodes.

Abstract: Provided is an LC composite component having a multi-layer substrate, a pattern coil, and a chip capacitive element. The multi-layer substrate is configured such that insulating layers are stacked. The pattern coil forms a coiled shape of which the coil axis extends along a stacking direction of the multi-layer substrate, and includes a coil conductor disposed between the insulating layers. The chip capacitive element includes a ceramic body having a relative permittivity higher than that of the insulating layers and counter electrodes. The chip capacitive element is at least partially disposed within the pattern coil.

Abstract: A silicon alignment pin is used to align successive layers of components made in semiconductor chips and/or metallic components to make easier the assembly of devices having a layered structure. The pin is made as a compressible structure which can be squeezed to reduce its outer diameter, have one end fit into a corresponding alignment pocket or cavity defined in a layer of material to be assembled into a layered structure, and then allowed to expand to produce an interference fit with the cavity. The other end can then be inserted into a corresponding cavity defined in a surface of a second layer of material that mates with the first layer. The two layers are in registry when the pin is mated to both. Multiple layers can be assembled to create a multilayer structure. Examples of such devices are presented.

Abstract: Provided is a circuit protection device including a plurality of sheets selectively formed with at least one coil pattern, at least one withdrawal electrode, at least one hole filled with a conductive material, and at least one capacitor electrode and at least two inductors and at least two capacitors, in which the at least one coil pattern forms one inductor and a capacitor is formed between the capacitor electrode and the coil pattern.

Abstract: A particular device includes a substrate and a spiral inductor coupled to the substrate. The spiral inductor includes a first conductive spiral and a second conductive spiral overlaying the first conductive spiral. A first portion of an innermost turn of the spiral inductor has a first thickness in a direction perpendicular to the substrate. The first portion of the innermost turn includes a first portion of the first conductive spiral and does not include the second conductive spiral. A second portion of the innermost turn includes a first portion of the second conductive spiral. A portion of an outermost turn of the spiral inductor has a second thickness in the direction perpendicular to the substrate that is greater than the first thickness. A portion of the outermost turn includes a second portion of the first conductive spiral and a second portion of the second conductive spiral.

Abstract: A transformer includes a first coil spiraling inwardly in a second direction. A second coil spirals along the first coil on the outside relative to the first coil. First and second external electrodes are provided in third and fourth directions relative to a first line passing through a gravity center of the first coil and an outer end thereof, respectively, the third direction being perpendicular to the first line, and the fourth direction being opposite thereto. First and second lead-out conductors are connected to the outer end of the first and the second coil, respectively, and electrically connected to the first and the second external electrodes, respectively. Both coils spiral along each other throughout their lengths. By spiraling in the second direction, the first coil is, at the outer end, oriented in a fourth direction.

Abstract: The present invention relates to a noise sensor for an alternating or direct current power supply. The sensor comprises a noise sensing unit and a noise separator. The noise separator is configured to receive first, second and third input signals and provide a first output signal representative of the common mode noise and a second output signal representative of the differential mode noise. The noise sensing unit comprises a first capacitive element, a second capacitive element, a first resistive element and a second resistive element.

Abstract: The present invention relates to a common mode filter and a method of manufacturing the same. In order to implement a common mode filter with low shrinkage, high substrate sintered density, and high strength, the present invention provides a common mode filter including: a lower substrate; an insulating layer having a conductor pattern inside and provided on the lower substrate; an upper substrate provided on the insulating layer; and a ferrite core made of ferrite and provided in the center of the insulating layer, the lower substrate, and the upper substrate by penetrating the insulating layer, the lower substrate, and the upper substrate, and a method of manufacturing the same.

Abstract: A modular jack has a magnetic assembly including insulative body, two rows of terminals retained to the insulative body, four transformers, and four common mode chokes. Each of the transformer and common mode choke includes a magnetic core and a plurality of conductive wires wound therearound. Each terminal has a recess for receiving an end portions of a corresponding wire and then the terminal is inserted into a through-hole of an internal printed circuit board for dip soldering. Guiding of the wire to the recess can be automated in contrast to manual winding operation.

Abstract: A system, hybrid common mode choke, and method are described herein. The system includes a differential signal transmitter and a differential signal receiver. A differential signal transmitter ground and a differential signal receiver ground are electrically disconnected in a manner that enables a common mode filter. The transmitter ground and the receiver ground may be coupled using an inductor, a resistor, a capacitor, or any combination thereof.

Abstract: An electrical connector includes a dielectric housing with a plurality of filtering modules therein. Each filtering module has a housing and a magnetics assembly including transformer cores with wires wrapped therearound. An array of pins extend from the module housing for connection to the wires. A plurality of tails extend from the module housing for interconnection to a circuit board upon which the connector may be mounted. An interconnection is provided between the pins and tails that may include filtering or other signal modifying circuitry. A circuit member having an enhanced layout is also provided for use in or upon which the connector may be mounted.

Abstract: A dongle transceiver a substrate, a transceiver circuit, a transmit/receive switch, a MIMO antenna structure, and a decoupling module. The transceiver circuit is on at least one of the first and second sides of the substrate and is coupled to the transmit/receive switch. The MIMO antenna structure is on at least one of the first and second sides of the substrate. The decoupling module is on at least one of the first and second sides of the substrate, couples the MIMO antenna structure to the transmit/receive switch, and electrically isolates antennas of the MIMO antenna structure.

Abstract: Active EMC filter connectable between an electric power source and an electric load. The filter has capacitors (C×N, C×U) connected between active conductors of the power source and a star point electric node. A filter capacitor (Cst, CstU) is connected between the star point and ground. A half-bridge has two switching devices (T3, T4; T1, T2) connected in cascade between a positive supply voltage and a negative supply voltage. A smoothing circuit (RgN, LgN; RgU, RgU) is connected between a common node of the switching devices and the star point. A control unit (Drive_N, Drive_U) drives the switching devices (T3, T4; T1, T2) digitally either in an ON-state or in an OFF-state, such as to limit a leakage current.

Abstract: There is provided a thin film-type coil component having a size equal to or less than 0806 and including a ceramic main body, external electrodes including a plurality of first external electrodes formed on one surface of the ceramic main body and a plurality of second external electrodes formed on the other surface facing one surface of the ceramic main body, and a coil unit including a plurality of coil layers stacked in the ceramic main body, thereby obtaining low direct current (DC) resistance.

Abstract: Embodiments of the present disclosure are directed towards a circuit board having integrated passive devices such as inductors, capacitors, resistors and associated techniques and configurations. In one embodiment, an apparatus includes a circuit board having a first surface and a second surface opposite to the first surface and a passive device integral to the circuit board, the passive device having an input terminal configured to couple with electrical power of a die, an output terminal electrically coupled with the input terminal, and electrical routing features disposed between the first surface and the second surface of the circuit board and coupled with the input terminal and the output terminal to route the electrical power between the input terminal and the output terminal, wherein the input terminal includes a surface configured to receive a solder ball connection of a package assembly including the die. Other embodiments may be described and/or claimed.

Abstract: Apparatus, methods, and systems for filtering for power line communications are described. In one example, a low pass filter for power line communication in a power system including at least one phase conductor and a neutral conductor is described. The filter includes at least one capacitor coupled between the phase conductor and the neutral conductor, at least one resistor coupled between the phase conductor and the neutral conductor, and at least one inductor coupled on the neutral conductor.

Abstract: A high-frequency swinging choke has at least two rod cores arranged next to one another in the longitudinal direction. The rod cores each have at least one winding. The windings are connected in series.

Abstract: An inductive filter for a magnetron power supply lead comprises an electrically insulating tube; a power lead located partially within the electrically insulating tube, and coaxial therewith, for supplying power from a magnetron power supply to a magnetron, a first core of a first magnetic material and a second core of a second magnetic material coaxially located on the electrically insulating tube; an insulating disc of same external diameter as the first core and the second core and coaxially located on the electrically insulating tube between the first core and the second core. The inductive filter is arranged to filter noise of a first frequency band and noise of a second, different, frequency band different from being transmitted along the power lead and to absorb a predetermined transient voltage from being transmitted along the power lead.

Abstract: A Universal Serial Bus (USB) apparatus for USB communication is provided. The USB apparatus includes a Printed Circuit Board (PCB) including a circuit for communicating data with an external device according to a USB communication standard, a connector for connecting to a USB terminal of the external device, and a noise reduction circuit connected between an output terminal of the PCB and the connector for reducing noise of a data signal. The noise reduction circuit includes a common-mode filter for removing harmonic components generated between a ‘+’ data signal and a ‘?’ data signal and passing the ‘+’ data signal and the ‘?’ data signal, which operate in a differential mode.

Abstract: In a common mode filter, at least one common mode filter portion is provided for removing a common mode noise, and has a first terminal pair configured to include first and second terminals connected to first and second external terminals, respectively, and has a second terminal pair configured to include third and fourth terminals connected to third and fourth external terminals, respectively. The filter includes an inductor circuit including at least two inductors that are connected in parallel to the first terminal pair of the common mode filter portion and are connected in series to each other, and an external terminal connected to the connection point of the at least two inductors. The external terminal is for being directly or indirectly grounded.

Abstract: A passive component with temperature compensation and an electronic device using the same are provided. The electronic device includes a central processor unit (CPU), a filter and a power conversion circuit. The filter includes the passive component and a variable resistor. The passive component includes an inductor and a negative temperature coefficient (NTC) resistor. The NTC resistor is contacted with a surface of the inductor, and the NTC resistor and the inductor are disposed in a package. The power conversion circuit provides a current information to the CPU according to a partial voltage difference of the filter. The power conversion circuit controls an output voltage through the filter according to a first control signal of the CPU, so as to provide the output voltage. The electronic device further includes an embedded controller. The embedded controller controls the variable resistor according to a second control signal of the CPU.

Abstract: A passive filter for connection between an AC source and a load, in either three-phases or in a single-phase arrangement. The filter includes, for each phase, a trap circuit having an inductor in series with a capacitor, the trap circuit having at least two terminals. A line reactor is connected between the AC source and the load, the line reactor having at least an input terminal, an output terminal and a tap terminal. A switch selectively connects at least one of the trap circuit terminals to a selected one of the line reactor terminals. The switch is capable of selecting which of the trap circuit terminals to connect to which of the line reactor terminals on the basis of a level of voltage distortion being experienced by the AC source, or on the basis of a calculated level of background voltage total harmonic distortion.

Abstract: A vehicle-mounted noise filter which suppresses electric field coupling between input and output terminals in the FM radio band, thereby allowing noise attenuation performance, which should originally be provided to a noise filter circuit, to be exhibited even in the FM radio band. The vehicle-mounted noise filter comprises a coil (1) obtained by winding a conductive wire around a magnetic core, input and output terminals (2, 3) electrically connected to both terminals of the coil, and a shielding member (4). The shielding member (4) is made of a conductive member which is grounded and disposed so as to shield the electric field between the input and output terminals (2, 3). The noise filter can also be configured using a capacitor having one terminal electrically connected to the coil (1) and the other terminal grounded.

Abstract: An alternating current (AC) power device includes an AC circuit having input nodes, output nodes and a ground node. The AC circuit is configured to receive an input electrical signal at the input nodes and generate an output electrical signal at the output nodes. The AC power device also includes an inductor coupled to the ground node of the AC circuit. The ground node is configured to be coupled to a ground plane at a ground potential. The AC circuit is configured to be coupled to a load at the output nodes. The inductor is configured to be connected in series between the ground node of the AC circuit and the load to attenuate radio frequency components present at the ground node.

Abstract: A transmission line includes a signal terminal for inputting a first signal and a second signal, a first wire coupled to the signal terminal for transmitting the first signal, a second wire coupled to the signal terminal for transmitting the second signal, a filtering module coupled to the first and second wires for receiving the first and second signals to filter out noises of the first and second signal, a third wire coupled to the filtering module for transmitting the first signal, and a fourth wire coupled to the filtering module for transmitting the second signal.

Abstract: Implementations are presented herein that include an antenna switch that includes a plurality of ports. A bandstop filter is coupled to at least one of the plurality of ports of the antenna switch and the bandstop filter is configured to attenuate a disturbing frequency. A transistor is configured to receive a control signal and to switch on the bandstop filter responsive to the control signal.

Abstract: There is provided a filter for receiving a rectangular or stepped source voltage to be filtered and for providing an output voltage, the filter including means arranged to determine the output voltage in dependence on the frequency components of the source voltage within the filter passband, and independent of output current drawn.

Abstract: An alternating current (AC) power device includes an AC circuit having input nodes, output nodes and a ground node. The AC circuit is configured to receive an input electrical signal at the input nodes and generate an output electrical signal at the output nodes. The AC power device also includes an inductor coupled to the ground node of the AC circuit. The ground node is configured to be coupled to a ground plane at a ground potential. The AC circuit is configured to be coupled to a load at the output nodes. The inductor is configured to be connected in series between the ground node of the AC circuit and the load to attenuate radio frequency components present at the ground node.

Abstract: A power supply system is disclosed that includes a first interleaved power supply, a second interleaved power supply, and a common electromagnetic interference filter. The common electromagnetic interference filter is configured to provide DC power from a DC power source to both the first interleaved power supply and the second interleaved power supply. In one example, the common electromagnetic interference filter comprises a localized filter stage configured to receive DC power from the DC power source, and a distributed filter stage configured to receive DC power from the localized filter stage. The distributed filter stage includes a first set of common mode capacitors electrically connected to and physically proximate input power lines of the first interleaved power supply, and a second set of common mode capacitors electrically connected to and physically proximate input power lines of the second interleaved power supply.

Abstract: The present disclosure relates to a circuit for mitigating EMI generated from an input terminal of an IC (Integrated Circuit) including a power input port connected to a first input and an operational mode selection port connected to a second input, the circuit including a first diode connected to the first input, an LC filter unit connectively interposed a cathode terminal of the first diode and the power input port, and a first resistor connectively interposed between the cathode terminal of the first diode and the second input.

Abstract: Provided is a circuit protection device including a plurality of sheets selectively formed with at least one coil pattern, at least one withdrawal electrode, at least one hole filled with a conductive material, and at least one capacitor electrode and at least two inductors and at least two capacitors, in which the at least one coil pattern forms one inductor and a capacitor is formed between the capacitor electrode and the coil pattern.

Abstract: A noise filter includes a first substrate on which a filter input terminal, an input-side capacitor, a common-mode choke coil, and a filter output terminal are mounted and a second substrate on which an output-side capacitor and a ground capacitor are mounted. The first substrate is selected from a plurality of first substrates including a substrate in which a characteristic of at least one of an input-side capacitor and a common-mode choke coil is different, the second substrate is selected from a plurality of second substrates including a substrate in which a characteristic of at least one of an output-side capacitor and a ground capacitor is different, and the second substrate is attached to an end of the first substrate so that the filter output terminal is electrically connected to the output-side capacitor and to be substantially vertical to the first substrate.

Abstract: A network signal coupling circuit installed in a circuit board and electrically coupled between a network-on-chip and a network connector is disclosed to include a coupling module installed each channel thereof, each coupling module including two capacitors respectively electrically connected in series to the two circuits of the respective channel, two sets of equivalent resistors respectively electrically connected in parallel to opposing ends of the capacitors, and two signal equivalent grounding terminals respectively electrically connected to the two sets of equivalent resistors; by means of the characteristic of the capacitors that the strength increases when the frequency rises, the signal coupling performance of the signal coupling circuit is relatively enhanced when the applied network frequency is increased.

Abstract: There is provided a filter for receiving a rectangular or stepped source voltage to be filtered and for providing an output voltage, the filter including means arranged to determine the output voltage in dependence on the frequency components of the source voltage within the filter passband, and independent of output current drawn.

Abstract: A high current RF choke network comprising a high current RF choke combined with an all-pass T-bridge filter. The high current RF choke may be connected to a grounded capacitor in the serial branch of the all-pass filter. In this case the parasitic capacitance of the RF choke practically becomes an integral part of the all-pass filter capacitor. The added capacitance in parallel to the parasitic capacitance of the high current RF choke practically neutralizes the resonances of the high current RF choke and thus extends significantly the operating frequency range of the network. The operating frequencies bandwidth range of the high current RF choke network is extended from the legacy range of 5 MHz to 1 GHz up to an extended range of at least 5 MHz to 3 GHz.

Abstract: A composite electronic component may include: an input terminal receiving power which has been converted by a power management unit; a power smoothing unit including a capacitor including a ceramic body in which a plurality of dielectric layers and internal electrodes are stacked such that the internal electrodes are disposed to face each other with the dielectric layer interposed therebetween and an inductor including a magnetic body including a coil part and a magnet, and smoothing power; and an output terminal supplying the smoothed power. The inductor may suppress an alternating current (AC) component of supplied power and the capacitor may reduce ripples in the supplied power.

Abstract: To pass an ultra high-speed differential signal and make it difficult to pass a common mode noise. Lumped—constant differential delay line DL is formed by arranging inductors Lo, being passive series elements, and capacitors Co, being passive parallel elements, in a differential four terminal network of a ladder shape composed of the passive series elements and the passive parallel elements arranged in differential lines 1 and 3. The lumped-constant differential delay line DL is composed of capacitors Co including two capacitors Co/2 and Co/2, or Co and Co equivalent to the aforementioned capacitors, having equal values, and connected in series. Inductors L1 to L4 for attenuating a common mode noise are connected between connection points of the capacitors Co/2 and Co/2 or Co and Co connected in series, and a ground potential, so that attenuation poles are formed for attenuating the common mode noise together with the capacitors Co/2 and Co.

Abstract: A magnetic interface circuit for interfacing between a cable side and a circuit side of a networking communication channel. The magnetic interface circuit includes a transformer and a 3-wire common mode choke (CMC). The transformer has a first winding connected to the cable side of the channel and a second winding connected to the circuit side of the channel. Each of the first and second windings has two output ports. The 3-wire CMC has a center winding and two outer windings respectively connected to the output ports of the first or second winding. The center winding has two opposite ends both used for connecting to ground.