Relays function like switches, letting one circuit control another. Several electrical components in your vehicle are controlled by relays, so knowing how to test them is essential. Luckily, the Drive’s crack information team has you covered!

If the coil is working properly, the meter will present resistance values between 50O and 200O. If the meter presents “OL,” then the coil is likely bad and needs to be replaced.

Line of Sight

The communication devices used by most of us in daily life transmit strong signals only when they have line-of-sight with each other. Satellite transmission, FM radio, TV channels and mobile networks all use line-of-sight communication to communicate across the horizon and behind obstacles.

Some of the returned photons hit objects hidden from the direct line of sight and are reflected back towards the relay wall surface. A fast photodetector, such as a Single-Photon Avalanche Diode array (SPAD), scans the surface of the relay wall and records the round trip time for all reflected light.

The resulting data can be used to reconstruct the hidden scene using one of several methods9,10,11. High-quality reconstructions require a fine time resolution (e.g., 100 ps). This requires a large area sensor to scan the relay wall and the signal must be decoded at a high rate to maintain this resolution. This limits the camera’s range of operation.

Access for Maintenance

If a site has a direct Internet connection, you can easily access the relay server to perform maintenance. The relay server comprises a secure system that Cisco Systems owns, manages and operates. The Telnet Connector program (tndconnect) is a command-line executable that provides terminal emulation over TCP/IP and connects your CSE to an external application on the relay server. The tndconnect session from your site to the relay server is mapped by the Cisco system, providing remote serviceability. The tndconnect session from the Cisco system to your site is also mapped, and technical support can troubleshoot problems at both ends of the tunnel.

The tndconnect program uses several command line parameters. For example, -port allows you to specify a port other than Telnet port 23, the default. This option can help you access the relay server if a firewall at your site blocks the standard Telnet port. The -verbose parameter logs debug messages and program trace information to a file. You can also use -timeout to specify a timeout in minutes after which the tndconnect session closes.

Antenna Structure Registration

The Federal Communications Commission requires owners of antenna structures that may create a hazard to air navigation because of their height, generally those more than 200 feet, or because of proximity to an airport to register those structures with the Commission. This registration process allows the FCC to fulfill its statutory responsibility for painting and lighting those structures in order to mitigate the hazards they pose to aviation.

In addition, local ordinances often require screening of antenna installations proximate to residential populations. This might include fencing, evergreen planting or earthen berms to lessen the visual impact of the structures. Screening requirements are common in radio tower locations and are sometimes also imposed on the bases of parabolic dishes.

FCC regulations also require the antenna structure owner or first licensee to maintain accurate ownership records in the Commission’s Antenna Structure Registration system. Failure to do so can cause confusion over ownership and ultimately detract from the ability of the FCC to resolve ownership/use conflicts in a timely manner, which could delay lighting outages or other maintenance activities.


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Pro Tip: Before you start to contact potential relay sites, get a high-resolution satellite image of the area you plan on covering. Look for buildings and foliage, and any trees with limbs that might interfere with your line of sight.

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