Field Report: FM Services TLM-1
The status outputs can be programmed to either high level or low level on alarm. However, I noticed that no alarm indication will be present if all power is lost to the system, unless the unit is programmed for alarm condition to be active high status output. An example would be if the site was without primary electrical power. Assuming the remote control system was on a UPS and could alert the operator with a status change to open for alarm when a power failure occurs, the site alarm will be sent. The summary alarm channel could be monitored by the remote control, and each of the status outputs can be monitored to determine the reason for a summary alarm.
A feature I like about the TLM-1 is the ease in which the unit can be reset for a change in the “normal” status. For example, assume one of the beacon lights has a failure of one bulb. This will trigger an alarm so the remote operator knows an abnormal situation exists. When a visual check confirms that all beacon levels are still flashing, the unit may be reset and it will be ready to alarm if an additional bulb, either a beacon or sidelight, goes out. This allows time to schedule a tower crew for relamping, but still be fully compliant in monitoring for additional outages.
I first evaluated this unit at an FM tower running analog and digital transmitters. The site had one side light bulb outage and also one beacon bulb outage, so it allowed me to evaluate each condition. The unit found these discrepancies within seconds of having calibrated for normal current operation. The second evaluation site was a directional AM, with transmitter power of 10kW at 750kHz. I've previously had sensor problems at this site with other brands of sensors due to the high RF levels. The TLM-1 operated flawlessly at this site also, although the only simulation I made this time was the loss of one sidelight. I'm sure the loss of a single beacon lamp would have also been detected. Initially, I was concerned since the unit is shipped from the factory in a plastic housing, but the circuit seems to be immune to AM radiation, at least to the level present at our 10kW transmitter site.
The status outputs and reset command input are all fed through opto-isolators, a good design feature. Personally, I would install the unit with ferrite beads on all wires connecting to the unit, but for this evaluation no RF suppression was used, and the unit performed well. The TLM-1 is manufactured by FM Services in Wilkesboro, NC, and questions about installation and operation were readily answered by telephone. I would recommend you consider this when the need for a tower light monitor arises, especially if you have a tower light circuit where a separate wire is not available for each sidelight and beacon level.
Mintzmyer is the president of The Praise Network, with AM/FM stations in Nebraska, Kansas, Colorado and South Dakota.
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