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Linking wireless to analogue 2-wire comms

A large number of venues and rental companies use Tecpro, Clear-Com, RTS-TW and similar analogue partyline (sometimes referred to as 2-wire) intercom systems. Many users find that two channels of intercom provide them with all the facilities they need and the only thing they would like to add is a small number of wireless beltpacks to allow selected users to move around freely. While walkie-talkies have their uses, they do not allow simultaneous 2-way (duplex) conversation to take place, so another solution is required.

The UHF full duplex wireless options are starting to age. They require a license to be legal and there is concern about the diminishing number of available frequency bands.

License-free operation is a popular option but intercom systems operating in the 2.4GHz band have generally gone out of favour because of spectrum overload issues that occur when the audience enter the venue carrying their smart phones which immediately start looking for a wifi connection.

There is now a reliable and affordable wireless option that will interface robustly with analogue 2-wire intercom and does not require a license in Europe, the USA, Japan or Australia. Green-GO DECT wireless intercom operates in the 1.9GHz band which does not suffer from the saturation issues that plague 2.4GHz. Conversation is full duplex, just like wired comms.

This remarkable system was designed by Green-GO Managing Director and PLASA Gottelier Award nominee, Joost van Eenbergen. It is manufactured in Holland alongside DMX and network products from ELC Lighting. Canford is the sole distributor in the UK and Ireland for both Green-GO and ELC products.

A few facts about Green-GO DECT wireless

  • DECT 1.9 GHz license-free wireless intercom
  • Full duplex, high audio quality, low latency
  • 2, 3 and 4 channel operation, selectable
  • Select from 32 channel options held in memory
  • RF coverage, around 50m - 300m depending on the environment
  • Increase RF range by adding remote antennas so beltpacks can roam
  • Rechargeable Li-Ion battery, removable, quick release (supplied)
  • 1-way battery charger with mini-USB (supplied)
  • Optional 6-way battery charger, mains powered, 1U
  • Register 4 beltpacks to single antenna
  • Register 4 antennas to single beltpack
  • Tough, lightweight ABS case
  • Comprehensive feature set

Unfortunately, linking Green-GO to analogue intercom is not as straight forward as it sounds because 2-wire analogue comms operates like an old style telephone system where all conversations are carried on a single pair of copper wires (hence the term 2-wire). This results in audio that has been injected from Green-GO on to the analogue line will immediately return and try to get back on to the Green-GO system, resulting in a nasty echo….

The echo problem is resolved by a clever process called ‘Nulling’ that analyses the unwanted returning signal, and works out the best way to cancel it out.

System Power and Communication

  • Green-GO digital devices communicate with each other over a data network.
  • All Green-GO devices need DC power

DC voltage is sent down the same cat5 cable that supplies the data. This is Power over Ethernet, commonly referred to as PoE and is supplied by a PoE ‘Switch’ which has several powered ports. A single Green-GO device is attached to each port.

Notes:

  •   Unlike analogue comms, Green-GO beltpacks can’t be daisy chained as it would reduce the available PoE voltage.
  •   Wireless beltpacks don’t use PoE because they are battery powered

How to get started?  
To interface Green-GO to 2-Wire analogue comms you need the following:

  • A PoE switch with enough powered ports to support the number of Green-GO devices being used - you can use a PoE switch from Green-GO or any other good brand
  • One SI2W 2-Wire interface for each analogue comms circuit required (typically only one)
  • One WAA antenna (for up to four WBPX wireless beltpacks). Add more if required…
  • Up to 4 WBPX wireless beltpacks. Add more if required… don’t forget to add more antennas
  • A headset for each WBPX wireless beltpack

The supplied NRG quick release battery will give around 6 hours continuous use from a full charge. A single channel charger is included. Charging takes around 4–5 hours when fully depleted.

In a professional environment, it is good practice to add:

  • 1 x spare NRG battery per beltpack
  • 1 x BR6 6-way charger, 1U

Control software is available free of charge from the Green-GO website in either Mac or Windows format. Download it and experiment - you’ll get an insight into how easy it is to programme your system to get the best from your events.

For further information on Green-GO digital intercom contact product manager Mike Reay: mcr@canford.co.uk

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