Electronic Engineering Dictionary

Point-Of-Load. [POL] a term used to indicate that a voltage regulator [voltage source] is place near the load that requires the voltage. On a single Printed Wiring Board [PWB], Point-of-Load means that the regulator is placed right next to the components requiring the voltage [load], as opposed to having the voltage regulator separated on the other side of the PWB [as some design practices would indicate].

In a system the term Point-of-Load means the voltage regulation [generation] is done in the same system block, at the card level and not the IC level, it just depends on the prospective. In many cases the term Point-of-Load refers to the same thing as Point-of-Source [POS], as in the regulator is placed next to the source that requires it. Related; Manufacturers of Voltage Regulators.

Point-Contact Diode. A diode in which the end of a fine wire is pressed against a semiconductor. Used as a detector or mixer over the microwave region. A graphic of a Point-contact diode is shown on the page covering Terms used with Diodes. Also refer to Manufacturers of Diodes for a list of companies producing diodes.

Polar Relay. A dc relay in which the direction of movement of the armature depends on the direction of the current flow. Manufacturers of Relays.

Polarity. The condition in an electrical circuit by which the direction of the flow of current can be determined. Usually applied to batteries and other direct voltage sources. Two opposite charges, one positive and one negative. A quality of having two opposite magnetic poles, one north and the other south.

Polarized Shell. A connector shell having a non symmetrical shape so that two connectors will only mate in one direction, and can not be mis-mated.

Pole. The number of points at which current can enter a switch; for example, single pole, double pole, and three pole. Note that the number of poles in a switch is completely independent of the number of throws and number of breaks a switch makes. The number of completely separate circuits that can pass through a switch at one time. The sections of a field magnet where the flux lines are concentrated; also where they enter and leave the magnet.

Pole Piece. A piece of ferromagnetic material used to control the distribution of magnetic lines of force; that is, it concentrates the lines of force in a particular place or evenly distributes the lines of force over a wide area. The shaped magnetic material upon which the stator windings of motors and generators are mounted or wound.

Polling. A process where a controller attempts to identify the source of an interrupt request by interrogating the peripherals connected to it.

Polyphase. A term that describes systems or units of a system that are activated by or which generate separate out-of-phase voltages. Typical polyphase systems are 2-phase and 3-phase; their voltages are 90- and 120-degrees out of phase, respectively. This term means the same as MULTIPHASE.

3-Phase Sine-wave

Polyphase Transformer. A transformer designed to operate in a polyphase system.

Polyswitch. A trade name for a Polymeric Positive Temperature Coefficient (PPTC) component. A resettable fuse that decreases current flow as it heats up, protecting a device from an over-current condition. As the over-current condition is removed the Polyswitch cools down and returns to a low resistance state allowing normal current flow again; although power will need to be removed before the device 'resets'. A temperature sensitive, non-linear thermistor component that increases its resistance with increased current flow. Also refer to Manufacturers of Resettable fuses.

Polyswitch

Port. A connection point to an interface bus. A connector on a computer that receives an interconnecting cable from a peripheral device. Of a device or network, a point of access where signals may be inserted or extracted, or where the device or network variables may be observed or measured.

Position Sensor. A component in a servosystem that measures position and converts the measurement into a form convenient for transmission as a feedback signal. [Sensor Manufacturers].

Position Servosystem. A servo-system whose end function is to control the position of the load it is driving.

Positive Clamper. A circuit that clamps the lower extremity of the output wave-shape to a dc potential of 0 volts.

Positive ECL. [PECL] Emitter Coupled Logic using a power supply [Vcc] other than -5.2 volts. Normally PECL is using a 5 volt power supply. Also refer to ECL Manufacturers for design data.

Positive Feedback. Feedback in which the feedback signal is in phase with the input signal. Also called Regenerative Feedback, in which part of the output is returned to the input increasing the input signal.

Positive Logic. The form of logic in which the more positive logic level represents 1 and the more negative level represents 0. The opposite of Negative true logic.

Positive Logic XOR Gate Symbols

Positive Temperature Coefficient. [PTC] The characteristic of a conductor in which the resistance increases as temperature increases.

Post Amplifier. A gain stage.

Potential Difference. The voltage between two points.

Potential Energy. Energy caused by the position of one body with respect to another body or to the relative parts of the same body.

Potentiometer

Potentiometer. A variable resistor, used as a volume control or a position sensor in servo-systems, having a terminal connected to each end of a resistive element and a third terminal connected to a wiper contact. The output is a voltage that is variable depending upon the position of the wiper contact. The potentiometer is commonly referred to as a variable voltage divider. It, in effect, converts mechanical information into an electrical signal. Also refer to the Resistor Dictionary, or Potentiometer Characteristics, or Potentiometer Manufacturers.

POTS. Plain Old Telephone Service. An acronym used to describe normal residential phone service.

Potting. The encapsulation or covering and filling in any voids of an electronic component. A process for encasing a part or an assembly of discrete parts within a protective material which is generally over 2.5 mm thick, varies in thickness, fills the connecting areas within an assembly, and requires a mold or container to confine the material while it is hardening. Potting is an embedding process where the protective material bonds to the mold or container so that it becomes integral with the item.