Atrax Control is not aligned with any particular equipment supplier. The following links have been provided to give you a starting point if you're looking for control system related items. As Atrax Control is an Australian company, these links concentrate on Australian suppliers.
Atrax Control does not necessarily endorse the products or services below - nor does it have anything against any that may have been left out.
Schneider - Modicon, Square D, Telemecanique and who knows what else.
Automation Direct Low cost Koyo-type PLCs (and other equipment). I don't want to stick my neck out and say they're the best value of any low cost PLC — there are so many options in the marketplace now and it depends on what you want — but they are definitely worth a look.
Prosoft — One of the most well-known companies in the field with a very wide range of gear. I've used lots of their stuff over the years. It can be somewhat expensive but is very reliable.
Digi - I have used their Digi One IAP protocol converter and found it to be reliable and good value for money. Incidentally, one of Digi's people has an extremely helpful blog on Industrial Protocols over IP.
Miille Applied Research have a range of protocol converters which handle a large number of weird protocols. I have used their 1771-rack-based Conitel (a particularly difficult protocol to deal with) protocol converter successfully. Miille's range now hasn't been updated for many years and their rack-based AB modules are now essentially obsolete, however their DIN-rail mounted units are still usable and might be your best option for some of the more unusual protocols.
Hiprom (now taken over by Rockwell Automation) - I have used their GPS modules successfully.
I have also used protocol converters from a few other companies over the years, but as time has marched on, the equipment I was familiar with has been superseded and the companies have been taken over or changed names. It seems a bit silly to put in a good word for product X by company Y when neither exist any more, so I won't make any more recommendations.
DataTaker is a name that springs to mind. I particularly like the extremely versatile analogue inputs on their DT8* series; in addition to the usual voltage and current sources, you can also hook up RTDs, thermocouples, strain gauges etc. directly to a standard analogue input.
I have also used Advantec ADAM 6000 series Remote I/O modules (which are highly versatile things) with a PC for data logging applications.
Miri - Have been around for a long time in this field. Seem to be very popular in bore-field monitoring.
Elpro - have a long history of making radio modems and telemetry units and are still going strong.
Power Supplies and Conditioning
Power Box all supply a wide range of power supplies and related equipment.
Erico feature the popular Critec surge arresters.
Novaris have a good range of lightning protection equipment. I particularly like their PP10 power surge arresters for computers and SL series (somewhat expensive but very compact) surge arresters for control wiring.
My recommendation for industrial ethernet is to use redundant networks if at all possible, and use equipment from different manufacturers in each network. These days, managed switches can be so complex that it's difficult for even these best manufacturers to completely guard against firmware-related problems which are likely to bring down multiple devices of the same type simultaneously.
Alloy once had a very good range of industrial switches and media converters, but now have branched out more into the IT field and their industrial range is much more limited.
Hirschmann have an extensive range of industrial switches and media converters. Fairly expensive, but generally regarded as very high quality.
Although D-Link are generally associated with consumer-grade equipment, they also make lots of high-end gear. These days, plant ethernet has grown to the stage where din-rail mounted switches (and even non-expandable rack-mounted 24 or 36 port switches) often aren't an option any more, and you need high capacity, stackable switches. In which case, consider D-Link.
I have used all of the above brands of equipment multiple times. While I've seen a some equipment failures amongst these brands, there are none that I would hesitate to use.
Automation Direct Stock a good range of miscellaneous control equipment (a lot of it is hidden under their "Motor Control" section) for very good prices. Unlike many other suppliers, they don't keep their price lists secret and they are extremely convenient to order from.
TC Direct are an on-line store specialising in temperature sensing. Like Automation Direct, they have a good range with good prices and are very convenient to use.
Citect - Probably the most popular PC-based SCADA package in Australia. Has now been absorbed into the Schneider empire.
Exigen (formerly Systems Reality) - I have worked with the Principle Engineer of this company and found him to extraordinarily skillful and knowledgeable.
MRA Electrical & Automation Engineering provide a wide range of services in the Electrical and Control Systems Engineering areas.