Acc+Ess Protocab has been in development for several years, the development team at Acc+Ess Ltd having spent a considerable amount of time researching options for a battery powered system, with a number of network engineers with experience in various fields being involved. We investigated the existing model railway standards in some detail and because they have been developed with track supply in mind, we did not at that time find a suitable standard for wireless use. We consider that it is not simply a case of replacing the power supply from the track with the power supply and control signals over the air.
In wire based control systems where a range of manufacturers may offer products for use, standards that these manufacturers provide for must be followed to ensure that the products can interact with other manufacturers' products over the same transmission medium (i.e. the track and control multiplexers). No such requirement exists for wireless based transmissions, and a locomotive and controller operating one manufacturer's systems can co-exist with a different manufacturer's control system in the same environment.
Also with a broadcast system, it is essential that the controller and the controlled locomotive are in constant check with each other and the loco able to respond rapidly to control signals and acknowledge that action has been taken. We therefore took the opportunity to design Protocab from the ground up, i.e. to determine what the modeller wants and needs and to create the system based on those findings and our technical understanding of the requirement.
In designing Protocab, we opted for the internationally recognised IEEE 802- standards using the 2.4GHz unlicensed spectrum. You will doubtless be familiar with the IEEE 802.11 standards for your Wi-Fi routers at home. These provide for the relatively infrequent transmission of large volumes of data, typically the full screen of your laptop computer. The amount of bandwidth required is substantial but easily handled by those routers. However, back in the day, the IEEE committee for 802 recognised the need for more infrequent transmission of small amounts of data, over much shorter distances and better suited to battery powered devices than 802.11 for instance.
The resulting standard is known as Local Personal Area Networks (Lowpan) and the standards are covered in IEEE802.15.4. The synergy between the standards within the 802 family lend ideally to the sort of applications that we will be placing before you as we develop the Protocab range. Because these are radio devices operating in the very busy 2.45GigaHertz spectrum, the standard provides all sorts of security mechanisms that prevent unauthorised or accidental interference.
Protocab automatically selects the best channel within the spectrum and therefore the question of selecting frequencies does not arise, and, because the Protocab controller and the devices on the locomotive(s) all have world-unique addresses, the 'adoption' of the locomotives' devices to the controller means that someone else's controller cannot accidentally or deliberately control your locomotives and vice versa.
As a manufacturer of radio transmitting and receiving devices, we are bound to comply with regulations for the use of these devices to make sure that our customers are safe and that our equipment does not cause harm, or is harmed by other radio devices.
We continue to monitor the development of alternative standards, the most recent development of Bluetooth, for example, itself part of the IEEE 802 family. We will introduce support for other standards, where practical and showing a clear advantage and, most importantly, permitting existing Protocab products to work harmoniously and effectively alongside the new standards.