SHoW DMX Features

Synchronized Hopping of FHSS Radio and DMX
CTI’s proprietary system synchronizes the FHSS (Frequency Hopping Spread Spectrum) hopping period so that (unlike other wireless DMX systems) every DMX data packet is transmitted completely during a single hop. Further, each DMX data packet is re-broadcast completely on the subsequent hop, and all of this happens during the period that the next DMX packet is arriving at the Transmitter. At the Receiver end, the packet (two copies) is received, checked and output as standard DMX with the same refresh rate as the original console output. Since each data packet is transmitted twice on different channels, the odds of a refresh being lost to local channel interference are significantly reduced.

High Speed Broadcast Data Rate with Optimized Data Format
The SHoW DMX Transceiver’s through-air data rate is 1Mbps, and the broadcast data packet has been optimized for half-duplex wireless DMX delivery so that the available 1Mbps through-air data rate is utilized as efficiently as possible. This allows the system to broadcast more than two times as many copies of the DMX data in a given period as was achievable with CTI’s previous system, the WDS Wireless Data System™. Each complete DMX packet (513 bytes with the start code byte) is transmitted in 5.5ms, four times faster than the fastest wired DMX data rate.
Adjustable Output Power
The SHoW DMX Transmitter has adjustable broadcast power from 5mW (FCC)/16mW (CE-ETSI) to 125mW (FCC)/395mW (CE-ETSI). This allows the user to adjust the output power to meet the application requirement. CE Units are limited at the factory to 32mW (FCC)/100mW (CE-ETSI) max output power.

The option of adjustable output power allows users to select only the power needed and to respect the wireless needs of their colleagues on their production, and other wireless users in the area. This philosophy is diametrically opposed to some other manufacturers who sell powerful radios with only one output setting designed to overpower all radio users in the area.

The WiSpy screen shots on the left show higher power in the left screen and lower power in the right screen.  Redder, denser dots indicate higher power. 

Adjustable Hopping Patterns, Including Full Bandwidth Hopping and Limited Bandwidth Hopping
SHoW DMX offers more than one kind of user-selectable FHSS hopping mode. In full bandwidth hopping mode, the system will continuously and pseudo-randomly hop between channels across the full 2.4GHz spectrum. This mode is available at any output power setting, and is quite typical of all FHSS radios.

In the Limited Bandwidth Hopping mode, the 2.4GHz band is divided into sub-bands. Each sub-band occupies approximately 40% of the full band, with one positioned at the low end, one in the center, and one at the high end of the full band. This allows the SHoW DMX Transmitter to be set to hop and broadcast in a different area of the spectrum to minimize or eliminate interference with WiFi or other channel specific or limited bandwidth equipment.

 

 

 

 

 

In these WiSpy screen shots, the effect of limiting the SHoW DMX bandwidth to WiFi bands 7-12 is clearly shown.  In the right hand screen, the portion of the spectrum below 2.466GHz is nearly devoid of activity.  Other WiFi signals could operate freely in that area.   

Limited Burst DMX Output
In Limited Burst mode, the user may select for broadcast any contiguous group of 30 or more DMX channels in multiples of 32 channels. These may be assigned to any starting address that will accommodate the burst size. This will reduce the amount of radio energy that is broadcast, thereby reducing the potential for interference with other systems. For instance, if a show needs only 128 channels of wireless DMX, the system can be set to broadcast only 128 channels, causing the radio to go silent 75% of the time (1-(128/512)=.75). If only 64 channels are used, the radio will be silent 87% of the time. This silent time reduces overall radio spectrum activity and increases the chances of all other radio signals in the vicinity to be broadcast successfully.
 

 

 

 

In these screen shots it can be seen that while operating at full 125mW power, but limited to an output of 30 DMX channels,  SHoW DMX has a very small radio footprint.  Some shows don't require all 512 channels to be broadcast via wireless, and this is an excellent option to reduce radio interference with other users in the same venue. 

Simple Default Plug and Play Mode
The SHoW DMX system has a sophisticated user interface allowing complete control of a number of settings, but in its default mode, SHoW DMX is completely plug and play. In its factory mode, or by resetting factory defaults, Transmitter and Receiver will wake up in contact with each other and no other settings are needed unless the user chooses to make them. With all its sophistication, the SHoW DMX system is also one of the simplest systems available.

RDM
The SHoW DMX system uses RDM communications for all remote device control and configuration, or for any inter-device communication required. This provides an easily understood method for managing requirements such as Receiver strength and Dimmer address setting. RDM commands may be issued from an upstream RDM controller such as a console, the SHoW DMX Monitor, or from the Transmitter.

RDM features include:

  1. RDM Controller Functions: Transmitters have some RDM controller functions accessible via the user interface.
  2. RDM Proxy Functions: Transmitters and Receivers act together as an RDM proxy system, providing a bi-directional half-duplex RDM link between the controller and any RDM device being controlled via the SHoW DMX system.
  3. RDM Discovery/Unique Device IDs: Each unit is programmed with a unique RDM device ID that will identify the unit, permitting RDM discovery, as well as communication with and control of each specific device.
  4. Receiver Received Signal Strength: System remotely polls each Receiver for its received signal strength via standard RDM.
  5. RDM Responder Features: SHoW DMX Dimmers have appropriate RDM features such as discovery, DMX addressing, battery power status, etc.
 

 

 

 

 

 

 

SHoW DMX has an excellent full implementation of RDM.  Unlike some other products that claim to be "RDM ready", SHoW DMX is fully RDM right now. 

ACN/Art-Net
The SHoW DMX Transmitter is provided with an RJ-45 connector and additional processing capacity to allow ACN and Art-Net implementation.