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The DCC Glossary!Under Construction!Please send any suggestions for additions, corrections, improvements to sprog@sprog-dcc.co.uk.A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 2 Digit Address: See Address. 4 Digit Address: See Address. 7 Bit Address: See Address. 14 Bit Address: See Address. 14 Step: See Speed Steps. 28 Step: See Speed Steps. 128 Step: See Speed Steps. Address 0: Not a valid locomotive address but used to indicate to the Command Station that you wish to control a DC locomotive (ie a locomotive with no Decoder fitted. Only one DC locomotive can usefully be controlled this way, if there is more than one DC locomotive on the track then they will all move at the same time. The command station modifies the DCC Waveform in such a way that the DCC packets can still be understood by decoders but the waveform has a DC offset causing a DC locomotive to move. The waveform is modified by making the 0 pulses in the waveform longer than usual and is known as zero stretching. Address: Each DCC Decoder and thus locomotive, in the case of multi-function decoders, has a unique address which is assigned to it during Programming. The default address for a newly purchased (or following factory reset) decoder is short address 3. Addresses can be either short (also known as 2 digit) addresses using 7 bits (see binary) or extended (also known as long or 4 digit) addresses using 14 bits. When counted in decimal, short addresses are valid in the range 1 to 127 but some DCC systems restrict short addressing to the range 1 to 99 leading to them being known as 2 digit addresses. Decimal extended addresses do not use the whole range available in 14 bits and are limited to the range 1 to 10,239 often further restricted by the DCC system to the range 100 to 9,999, or sometimes 1 to 9,999. Address Only Programming: See Programming. Acceleration: Accessory Decoder: See Decoder. Advanced Consist: See Consist. Asymmetric DCC: Automatic Reversing Module: A device used to auutomatically switch the polarity of the DCC track voltage on a reverse loop. As with traditional DC layouts, a problem exists in a DCC layout where a track turns through 180 degrees and connects to itself, resulting in a reverse loop. A short circuit can exist between the two tracks. ??? -reversing section Back EMF: A motor cab also be used in reverse as a generator. Whenever a motor is turning due to a voltage being applied, the generator effect causes a voltage of opposite polarity to be generated by the motor. This is known as Back Electro-Motive Force or Back EMF. If the drive voltage is removed momentarily, the Back EMF can be measured to give an indication of the speed of the motor. This measurement is used in feedback loop to keep the motor speed constant under varying load. It is sometimes referred to as "feedback" or "speed stabilisation". Bidirectional Communications: The ability of a decoder to transmit messages back to the command station or to a lineside decoder. Bit: See Binary. BEMF: See Back EMF. Block Occupancy Detector (BOD): See Occupancy Detector BOD: See Occupancy Detector Booster: An amplifier that takes the signal from the command station and feeds it to the track. Boosters are rated by the amount of current they can supply to the track. A booster may be built into the same enclosure as the command station. Most DCC systems allow additional boosters to be connected if the layout requires more current than can be provided by a single booster. Brake Generator: Brake on DC: Braking Section: Broadcast Packet: A Packet that will be recognized and acted upon by all Decoders, often used for Broadcast Stop to implement a Braking Section. Broadcast Stop: A Broadcast Packet that instructs all Multi-Function Decoders to bring the motor to a stop subject to Deceleration programmed in CVxxx. Bus: A collection of wires used to distribute electrical signals, usually between more than two points. See also Power Bus, Cab Bus, Loconet, XpressNET. Byte: See Binary Cab: ??? -handheld -tower Conformance Warrant: CV: See Configuration Variable DC: Direct Current. An electric current that always flows the same way. ??? See also Power Conversion DCC: Digital Command Control - What this Glossary is all about! DCC Friendly: DCC Waveform: The DCC signal on the track is an AC signal. The frequency varies with each cycle depending upon the data being transmitted to the track. Data is transmitted as a binary bitstream of 1s and 0s. A 1 is transmitted as a cycle of nominally 116us or approximately 8.6KHz (cycles per second). A 0 is transmitted as a cycle of nominally 200us or 5Khz. Deceleration: Decoder: ??? -silent drive - supersonic -stationary -mobile -accessory -locomotive -Multi-function Detection Section: See Occupancy Detector Detector: ??? could be -block -transponding -Railcomm Direct Bit Programming: See Programming Direct Byte Programming: See Programming Direct Mode Programming: See Programming Dither: A method of getting better low speed control of a motor by adding higher power pulses to the motor drive signal. Helps to overcome friction in the motor and drive train. See also Back EMF Dropper: Short length of wire used to connect the Power Bus to the track at regular intervals. See also How Many Wires?. Emergency Stop: Extended Address: See Address. Feedback: ??? Could be -transponding et, -BEMF -turnout position See also Feedback Bus Feedback Bus: Filter: A resistor and capacitor connected in series between the tracks, often at the furthest point from the booster. Removes high frequency noise form the DCC signal and can improve reliability and reduce runaways. Function: ??? -outputs -mapping Function Decoder: See Decoder. Function Mapping: See Function. Handheld: See Cab. LCB: See Layout Control Bus LED: Locomotive Decoder: See Decoder Long Address: See Address. Mobile Decoder: See Decoder Multi-Function Decoder: See Decoder NMRA: POM: Programming on the Main - See Programming. Portescap: Power Bus: The output of a booster is distributed around the layout using two thick, low resistance wires. Connection to the track is made at regular intervals using Track feeds or Droppers. See also How Many Wires?. Power Conversion: ??? See also DC Power District: A layout may be split into a number of power districts by isolating sections of track and feeding each from it's own booster or circuit breaker. If a layout is large and requires a lot of current to operate it, then multiple boosters may be used. Circuit breakers are used for fault containment such that a short circuit in one power district will not cause the power to be shut off in other power districts. Power districts may be formed by splitting the layout geographically (e.g. one ore more baseboards in each power district) or operationally (e.g. up and down lines in separate power districts). Power Routing Turnout: ??? Not generally a good idea Power Station: See Booster. Programming on the Main (POM): See Programming. Programming Track: See Programming. Programming: ??? -POM -service mode -track -modes PWM: See Pulse Width Modulation. RailCom: Registered trade mark of Lenz Elektronik, GmbH for thier Bi-directional Communication system, based on NMRA RP-9.3.1 Register Mode Programming: See Programming. Reverse Loop: See Automatic Reversing Module. Reversing Section: See Automatic Reversing Module. Reversing Module: See Automatic Reversing Module. Runaway: A loco that takes on a life of its own and "runs away" down the track ignoring the throttle. Service Mode: See Programming. Short Address: See Address. Snubber: See Filter. Signal Influenced Section: Silent Drive Decoder: See Decoder
Sound Decoder: Speed Stabilisation: See Back EMF. Speed Steps:Supersonic Decoder: See Decoder Stall Current: The current drawn by a motor when it is stalled or prevented from rotating. A Decoder should be capable of handling the stall current of the motor to prevent damage to the decoder in the event of the motor stalling. Stationary Decoder: See Decoder Terminator: See Filter.Throttle: Track Feed: See Dropper. Track Voltage: Transformer: A device that converts one AC voltage to another, Usually converting household mains voltage to a lower voltage, e.g. 12V. Transformer is sometimes used to refer to a complete power supply that also rectifies the AC voltage to produces a DC output. Transponding: Digitrax's version of Bidirectional Communications Uninterruptible Signal Processing: USP: See Uninterruptible Signal Processing. XpressNET: Trade mark of Lenz Elektronik, GmbH for the bus used to interconnect DCC modules such as the command station, cabs and computer interface. XpressNET is based upon the RS-485 standard and the protocols are freely available to industry and hobbyists. Zero Stretching: See Address 0. |