ADB 62.5 An old digital protocol developed by ADB. Still in use although not on new products. Uses a 5 pin XLR so don t confuse it with DMX512.

Transcription

1 The Guide by Artistic Licence ACN (aka Advanced Control Network) The ACN is the next generation control protocol which is under development by ESTA (Entertainment Services and Technology Association). It will operate using Ethernet and is intended to address the limitations of DMX512. Related products: DMX-Hub ADB 62.5 An old digital protocol developed by ADB. Still in use although not on new products. Uses a 5 pin XLR so don t confuse it with DMX512. AMX192 An old analogue protocol specified by USITT which is now hardly used. Uses a 4 pin XLR connector. Avab A digital protocol developed by Avab. It is not a fast as DMX512 but is still widely used. Connectors vary and the DMX512 5 pin XLR is often used. Balanced Signal A balanced signal is a way of transmitting data without picking up electrical interference. The original signal is transmitted along with an inverted copy of two wires which are twisted together (twisted pair). Any interference picked up by the cable will be picked up equally by both wires of the twisted pair. The receiver electronically subtracts the two signals from each other which removes the interference. DMX512 uses this method of transmission which is why three rather than two electrical connections are required. Base Address This is the DMX512 channel at which a device (Moving Lamp or Dimmer) will respond. DMX512 contains a total of 512 channels. if you are using a Moving lamp which needs 10 channels, setting the base address to 21 will make it use channels 21 to 30. You could then Patch the next moving lamp to channel 31. Baud (aka Bits Per Second) Digital protocols like the DMX512 transfer data at set rate which is measured in bits per second. It means the number of electronic signal changes per second. DMX512 operates at 250,000 Baud.

2 CMX A digital protocol developed by Colortran. It is not as fast as DMX512 but is still widely used. D54 An old analogue protocol developed by Strand. Still very widely used. Uses a 3 pin XLR although a 4 pin is sometimes used when compatibility with Avab is needed. Demultiplex (aka Demux) Demultiplexing consists of converting one signal into many. Usually this involves converting DMX512 into 0 to 10V control signals for older dimmer racks. Related products: DMX-Demux DMX512 This is the name of the digital protocol used to carry lighting control data between the lighting desk and the dimmers or moving lights. It should be connected by a 5 pin XLR connector although a lot of moving lamp manufacturers use the 3 pin XLR. The wiring is the same for both: Pin 1 Ground (connects the cable to the screen) Pin 2 Data minus (connects to one wire of the twisted pair) Pin 3 data plus (connects to the other wire of the twisted pair) It is best to leave Pins 4 & 5 unconnected as there are compatibility problems between different manufacturers. The console has the female output connector. Related products: Almost all Artistic Licence products DMX512 (1990) The protocol was changed slightly in The Mark After Break value was increased to 8uS. In reality, this is seldom an issue. Related products: Almost all Artistic Licence products Ethernet Ethernet is another digital protocol used for communication between equipment. t comes in a number of flavours, al of which include the word Base, for example 10BaseT. The different flavours use different connectors and operate at different data rates. Ethernet is starting to be used in the Entertainment Technology Industry for sending large amounts of control data when DMX512 is too slow. The most important flavour is 10BaseT which uses the RJ45 (European telephone) connector. Related products: DMX-Hub

3 Htp (aka Highest Takes Precedence) This refers to the way in which a lighting signal is controlled. When that channel is controlled by more than one source (for example, if two sub-masters on a lighting desk contain the same channel) the highest value is used. Htp channels are normally used for controlling intensity. Isolation (aka Optical Isolation aka Galvanic Isolation) This is method of transferring data between equipment without making an electrical connection. The signal (DMX512 or MIDI) is converted into light then back to an electrical signal. Without isolation all of the electrical equipment is electrically connected together. This is not a problem for small rigs, but as the distances between the equipment grows problems can occur. If, for example, the lighting console and the dimmer rack are powered from different phases, sub-stations or generators, an equipment fault could cause large currents to flow down the control cable. A couple of volts difference in mains earth between the console and the dimmers is enough to cause serious damage. isolation solves this problem by ensuring that there is no electrical connection between the equipment. Splitters are often used to introduce an isolation barrier in the DMX512signal. Some splitters just isolate the input whilst some isolate all of the individual inputs. If all of the equipment in a system has isolated inputs there is no need for the additional expense of Splitters with isolated outputs. Related products: DMX-Split, Rack-Split, Iso-Split Loop through Most DMX512 receivers will have two DMX512 connectors so that you can loop through a cable to the next receiver. Normally the Loop Through connectors are simply wired together inside the receiver. Don t try to loop through more than about 30 receivers as above this the DMX512 signal will run out of current. The final loop through connector must be terminated. Ltp (aka latest Takes Precedence) This refers to the way in which a lighting channel is controlled. When that channel is controlled by more than one source (for example if two sub-masters on a lighting desk contain the same channel) the last value to change is used. Ltp channels are normally used for controlling non intensity channels such as pan and tilt. Merge Merging data is a method of allowing two lighting consoles to output onto the same DMX512 cable. This is used when, for example, two lighting consoles must control the same dimmer rack. Related products: DMX-Merger, Protocol-Converter, DMX-Mux, DMX-Dongle, No- Worries

4 MIDI (aka Musical Instrument Digital Interface) This is a digital protocol designed to allow Musical Instruments to communicate. It is used frequently in lighting control for remote control. It connects via a 5 pin DIN connector. There are many different types of information transmitted on MIDI so don t assume that equipment can talk just because they both have MIDI connectors. MIDI equipment is usually supplied with an Implementation Sheet which will show whether two pieces of equipment are compatible. Related products: MIDI-Scope, MIDI-DMX Multiplex Multiplexing consists of converting many signals into one signal. Usually this involves converting the 0 to 10V multicore outputs of a lighting desk to DMX512. Related products: DMX-Mux S20 An old analogue protocol developed by ADB. Still in use although not on new products. Uses a 5 pin DIN so don confuse it with MIDI. Splitter This is an electronic device which is used to provide multiple outputs of DMX512 from a single input. It is used when the show has a lot of dimmers or moving lamps which each require a DMX512 input. It is usually a bad idea to connect more than 30 DMX512 inputs as each receiver takes a small amount of power fro m the signal. Each output from a Splitter will drive as many receivers (moving lamps, dimmers) as the original DMX512 signal. Related products: DMX-Split, Rack-Split, Iso-Split Terminator (aka Term) This is a male XLR connector which contains a 120 ohm resistor wired between pins 2 & 3. The terminator is plugged into the final loop through connector of the DMX512 daisy chain. It is needed to stop electronic reflections in the cable which would corrupt the data. Many small lighting rigs seem to work fine without terminators, but don t take the risk because the problems will start when the curtain goes up! Related products: DMX-Term

5 Timecode Timecode is the general term given to sending time information between equipment so that they can synchronise together. There are many different types: VITC - Vertical Interval Timecode is incorporated into a video signal LTC -Longitudinal Timecode can be recorded on audio tape or CD or transmitted as an audio signal. I comes in four flavours: Film - operates at 24fps and is used by the film industry EBU -operates at 25 fps, the European video standard SMPTE - operates at 30fps, one of the US video standards DF - Drop Frame operates at 29.97fps, the other US video standard MTC - MIDI Timecode operates at any of the frame rates above and is transmitted over a MIDI cable. Related products: Timecode-Transcoder Y-Chords This is a cable which splits one output into two outputs by simply wiring two cables into one connector. These cables are a very bad idea when working with a digital protocol like DMX512. The cable allows the signal to be sent down two cables which causes electronic reflections and corrupts the data. Use a Splitter instead.