This is an old revision of the document!
An integrated circuit (IC) is an electronic component which typically packages a collection of transistors, diodes and resistors to perform some useful function. There are numerous types with many package configurations. You may be familiar with fairly simple ones like Operation Amplifiers (Op Amps) or “555” timers, or complex types like microprocessors. Modern ICs are generally encased in a square/rectangular plactic package with many leads/pins. Pins are commonly spaced on a 0.1“(2.54mm) grid which will fit the holes on stripboard and breadboards. This packaging is usually referred to as Through Hole mounting as the pins normally go through holes in a PCB. Newer ICs can be found with much closer pin spacings and very small packages, usually designed for surface mounting on PCBs.
A means whereby microprocessors (PICs and other types), may be programmed while mounted in the circuit they are intended to control. There are no standard physical designs/pinouts used for in-circuit programming. Many MERG modules using PIC microprocessors are provided with an ICSP connector with a pinout for the popular PICKIT programmer.
Pinout shown here.
Incandescent lamps emit light when an electric current passes through a thin wire filament, which becomes very hot and glow brightly. Filament lamps may have a shorter lifetime than most electronic components because the filament could melt at a weak point. Incandescent lamps, such as the tiny “grain-of-rice or grain-of-wheat” lamps shown in the second image, have been used for decades as model engine lights, signaling lights and for layout structure lighting. There is a movement to replace incandescent lamps with light emitting diodes (LEDs) which use less power, generate less heat and typically last longer.
An inductor is a coil of wire which may have a core of air, iron or ferrite (a brittle material made from iron). Its electrical property is called inductance and the unit for this is the Henry, symbol H. 1H is very large so mH and uH are used, 1000uH=1mH and 1000mH=1H. Iron and ferrite cores increase the inductance.
Inductors are mainly used to tune circuits and to block high-frequency AC signals (they're sometimes called chokes)
They pass DC easily, but block AC signals; this is the opposite action to a capacitor.
Description used by UK track manufacturer, PECO, to denote turnouts manufactured with an insulated crossing (frog). This avoids the need for polarity switching for the crossing at the expense of poorer current collection for locomotives.
Name for a means of linking the operation of points and signals such that signals can only show a proceed aspect when points are correctly set, and that points cannot be moved unless the signals over them are showing stop aspects. Interlocking can be mechanical, electrical using relays or carried out by computers.
An Interrupt Service Routine is a firmware/software program subroutine (sub-program) triggered by a microprocessor hardware pin. When triggered, the processor will temporarily execute a subroutine then return to the previous program execution. An ISR can be used to make the processor immediately take care of a time critical operation. While there are many uses for an ISR, some common uses would be for receiving serial bits from a serial data interface or sensing an external clock signal to trigger the sending of video signals at a precise time. In some cases there are more than one interrupt trigger pin or indication. Because of this there may be priority settings. A High priority interrupt cannot itself be interrupted whereas a Low priority interrupt can be interrupted by a High level one. This helps keep multiple ISRs from interfering with each other.