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To the Rescue at Farm Radio Network

User Report: Broadcast Tools’ Site Sentinel-4 Eases Remote Monitoring

Michael Bradford, CPBE is owner of and senior engineer with Broadcast/Audio Services

JACKSON, Mich. — Tucked into a corner of the transmitter room at WILS(AM) in Lansing, Mich., are two Middle Atlantic equipment racks full of equipment that constitute the uplink for the Michigan Farm Radio Network.

This satellite delivery provider began almost 30 years ago in the corner of a parking lot in Milan, Mich. and served affiliates with farm market news that impacted a tri-state area.

When Saga Communications purchased the system and moved it to the Lansing location, the expansion of services soon included uplinking the Detroit Tigers, Lions, Pistons and Red Wings. Then followed the Illinois Radio Network with studios in Chicago, and most recently, the Minnesota News Network, with its main studios in Minneapolis/St. Paul.


For years my client, WILS, has depended on Broadcast Tools equipment to permit dial-up audio monitoring, remote switching and, most recently, Internet-based control of reboot functions for two Comrex Nexus ISDN codecs using the Broadcast Tools Web Switch. It soon became obvious that they needed more capability than existed with the previous dial-up units.

Engineer Ralph Haines (a contract engineer, like me), Michael J. Ostlund from the Minnesota News Network, Dennis Mellott, Saga’s GM in Lansing, Stephen Paul from the Saga Detroit office and I put our heads together to plan a system that would permit access to all five affiliates’ T-1, ISDN, dial-up and alternate program systems. This is where the Broadcast Tools Site Sentinel-4 entered the picture.

The recent installation of a high-speed Internet connection into the uplink site to accommodate our Web switch opened up a new venue for remote control and monitoring.

The Site Sentinel-4 is a cost-effective, one-third-rack size device for Web-based remote control, monitoring, status alerts and relay interface with other equipment from virtually anywhere you have access to the Internet. This includes the newest Web-capable handheld devices.

Reviewing the capabilities gave me the impression that the designer had been sitting in on our brain-storming sessions.

Here was a “tool” that included analog metering for four separate channels, status monitoring for four channels, four logic relay interfaces for direct interface with other equipment, a stereo silence sensor, a built-in power loss detector, a separate set of contacts for remote power control via a third-party device and an optional temperature probe. These features are programmable to accommodate user requirements.

Every feature of the Site Sentinel-4 can be accessed over any IP network, including a private network, IP-based industrial control network and, of course, the Internet. It also features a logging system for parameter snapshots, alarms, status, metering and temperature sensing that will e-mail anyone of eight recipients with routine metering and/or alarm situations.

The Site Sentinel-4 is equipped with four buffered high-resolution 10 volt metering (analog) channels, four optically isolated status/logic channels configured for 5 to 24 VDC “wet” or “dry” inputs (user selectable with jumpers), four channels of SPST 1-amp relays that may be latched on or off or pulsed with user-defined timing.

It also features a separate, isolated relay with user-selectable contact assignment to interface with an external device, such as Middle Atlantic’s RLM-15-1C, 20-1C or RLM30-L530-1 AC controller devices to turn higher-current external equipment “on,” “off” or “reboot” as required. SNMP and SMTP username and passwords are supported.

Because each channel of control can be password-protected, it is possible to assign security clearance for each of the four affiliates at the MFRN uplink with its own password. This permits everyone to monitor what’s going on at any time, but limits control functions to those with specific password authority.

The system has the features we’ve come to expect from Broadcast Tools: Euroblock screw terminal connections for metering, status/logic, control relays and the stereo silence sensor. There are two power supply jacks; one for the power input to the unit and another for the optional “loss of power” input.

The temperature probe input is a 1/8-inch TRS jack for the optional probe, programmable for Fahrenheit or Celsius indication. Front-panel LEDs indicate relay and status states, “local” operation (a nice safety feature when you’re connected to external high-power transmitters or other devices), rear-panel RJ-45 10/100base-T LAN/Ethernet interface, an RFI shielded enclosure and a surge-protected power supply.

The Site Sentinel-4 is one of the series of one-third-rack devices from Broadcast Tools that fits nicely into the optional rack-mount shelf. (I like to use the Furman Plug Lock power strip for the wall-wart power supplies. This device permits five separate wall-wart supplies to be secured into one rack-mountable plug strip.)

Two Cat-5E cables are included — one cross-over cable for direct connection to a PC to program the various passwords, channel labels and e-mail addresses for recipients, and another direct-connect Cat-5E cable for connection to your LAN or Internet switch. You can fabricate longer cables if needed. I chose to make a slightly longer cable with Cat-5E stranded cable and the Platinum Tools EZ-RJ45 connectors. The pass-through design of the EZ-RJ45 permits a quick check of the strand arrangement to confirm that two or more strands didn’t cross over before you crimp the connector.


An included CD has the Broadcast Tools product line for reference along with the PDF file of the installation and operation manual. You’ll also find a separate two-page “quick connection reference” guide, which I found sufficient to connect to my PC and make the basic programming, site-labeling and initial password assignments.

I called our ISP for the uplink to obtain the specific IP address, gateway, submask and related data necessary to program the Site Sentinel-4 for Internet connection, once I made the decisions for the various metering and status/logic channels.

For complete programming you will need the manual, as there are many options you’ll want to utilize, once you have discovered the versatility available to you.

For instance, each of our four affiliates is assigned a separate user name and password. This permits them to monitor all the metering and alarm channels, but have access to control functions exclusive to their particular network. The power failure alarm is “sent” to our main Ops Center in Lansing, with copies to me and engineering associate, Ralph Haines. We can access the site via Internet and determine what action is required.

I placed the temperature probe in the exhaust stream for the high-power amplifier at the uplink, and connected the power-loss power supply ahead of the UPS AC supply. Separate summary alarm contacts in the codecs connect directly to the Site Sentinel-4 and are programmed to send an e-mail to the particular affiliate’s engineer and our local engineers. We are planning on adding a nitrogen low-pressure alarm for the waveguide.

Because the four relays in the Site Sentinel-4 can be programmed for “on,” “off” or “pulse,” I use them to reboot those devices that seem to want to lock up for no apparent reason now and then. The connection to these devices is via the Middle Atlantic AC controllers mentioned.

The manual is clear and concise; questions have been addressed with “screen shots” of exactly what you will see on your PC monitor. Once you have made the changes desired, you must enter the final IP address information and power reboot the Site Sentinel-4 to set that data into its non-volatile memory. The device contains a recessed “reset” button in case you wish or need to return to the factory settings.

Now we can access the Site Sentinel-4 any time from any PC and change audio sources, check faults, extract an actual alarm/metering log and see at a glance the status of each carrier we uplink at this site. I am looking forward to the Site Sentinel-16, now available, for a planned expansion at the Michigan Farm Radio Network uplink.

For information, contact Don Winget at Broadcast Tools in Washington at (360) 854-9559 or visit