The sprawling California State Fair is just about to close in Sacramento and Bil Lowry will has been watching a key part of it - the carnival midway operation - through a set of computer screens monitoring a Wi-Fi mesh network.

The portable backbone network, which is often lashed into place using plastic zipties, is based on Firetide Networks' wireless LAN mesh nodes. It links some 300 Motorola handheld scanners and point-of-sale terminals to the midway's electronic ticketing, warehousing and time-card applications. It also interconnects other corporate applications and databases on Microsoft Windows servers and PCs in the mobile trailers that serve as the working, living, dining and sleeping quarters for 500 permanent and temporary workers.

"It's kind of an 'ER' approach to networking," Lowry says, describing a unique, high-pressure, fast-moving network. The permanent, four-person IT staff, augmented by four to six temporary workers culled from the local Craigslist, literally has tossed the wireless LAN documentation onto a shelf and left it there.

Lowry is the director of IT and marketing technologies for Ray Cammack Shows (RCS), which claims to be the largest carnival company in the United States. Nominally headquartered in Laveen, Arizona, near Phoenix, RCS is actually a travelling corporation for most of the year: A convoy of 80 trucks moves from site to site everything it needs, including ride machinery, equipment, employees, a complete IT infrastructure, a commissary, a hair salon and a warehouse-in-a-tent that stocks hundreds of thousands of toys and prizes for carnival attendees.

Lowry and his staff call the first-day opening of each venue "the launch."

"It really is like launching a rocket: it's rough, noisy, chaotic," he says. The push-to-talk radios are alive with chatter, complaints, problem reports, confusion and questions, and the net traffic load swells as the midway throngs with fun seekers lining up for games and rides, including the 12-story Le Grande Wheel, the biggest mobile Ferris wheel in the county (it takes up 18 semi-trailer loads by itself).

Everyone knows when the network "achieves orbit." "You go from constant chatter, to suddenly it's quiet," Lowry says. "And you're sailing. We can go days without any tech support problems."

The Sacramento network was put together in about 72 hours. Just days earlier, the carnival operation had dismantled itself in Costa Mesa, California, where RCS provided the midway attractions for the Orange County Fair. Since first setting up a Firetide mesh on a small test event last November, Lowry's team has honed its deployment skills.

Arriving at a new site, the crew winches up a 65-foot portable tower, not far from the main IT server trailer. The height lets RCS shoot wireless signals nearly a half-mile away to the separate KidLand venue. The tower mounts four Firetide HotPort 3000 series outdoor nodes, with their directional patch antennas covering different areas of the midway site. A fifth node acts as a backup unit. The antenna gives a clear line of sight to other Firetide nodes, mounted on metal poles usually attached to the numerous 8-by-9-foot metal ticket booths.

The nodes operate in a swath of the 5GHz spectrum, and their 400-milliwatt radios deliver strong, clear, resilient signals that can be precisely aimed. In Sacramento, Lowry's team is shooting one Firetide signal through a 20-foot tunnel between some trees and fairground structure. At another location, the fairground's monorail cars move through another signal: The mesh immediately adjusts, re-routing traffic as needed and then "heals itself" once the cars have passed by.

At the ticket booths, an Ethernet cable runs from the topside mesh node to a Firetide HotPoint (or in some cases a Cisco) access point inside the booth. The Firetide device incorporates a four-port Ethernet switch for point-of-sale terminals or other wired clients, while the 2.4GHz radio creates a wireless link for the Motorola 6090 handheld computer and scanner.

Wireless mesh and handheld scanners have transformed the carnival industry, says Lowry. RCS rival, North American Midway, also uses a Firetide mesh. Not too long ago, carnivals at day's end weighed instead of counted hundreds of thousands of greasy, dirty, sweat-sodden tickets. Thieves and ticket counterfeiters were an equally unsavory fact of life. And if any visitors lost their tickets, no refund was possible.

Today, midway visitors can pay electronically, and a software application creates an instant account for them. Instead of a roll of tickets, they get a bar-coded card: in effect, a debit card. The card is presented at each ride or game, scanned, and the account debited. If the card is lost, you present a receipt, and get a new card on the spot.

The scanners also manage the inventory of prizes or purchases made at the various venues, feeding the data to the inventory application. At a tent warehouse, employees scan cases and cartons as they're delivered and then again as they're sent out to the various venues. The same scanners are used to read a bar code on employee ID badges and the start and stop of each shift, the time data fed to the RCS payroll software.

The mesh installation is by now a well-rehearsed routine that places a premium on adapting to each new venue. Poles can be, and have been, lashed into place almost anywhere: against a chain-link fence or a truck. Especially in the early stage of deployment, the IT team cranks up small portable Honda generators to power a node, until more permanent lines can be run out. The team no longer bothers with Firetide's detailed instructions on protecting antenna joints or specifications on mountings. "We don't have the luxury of doing any of that," says Lowry.

The mesh and access points are monitored using Firetide's HotView Pro management application. The Motorola handhelds are provisioned and managed using WaveLink's Avalanche software.

Lowry has begun planning to deploy a separate video surveillance backbone, based on Firetide's more recent HotPort 6000 series indoor and outdoor mesh nodes.