Specifications

RFC-1 Installation page 3.13
3.6 Battery Backup and Clock/Calendar
All of the user options and programmable parameters of the RFC-1 are stored in non-volatile memory that remains
intact if power is interrupted. The clock/calendar requires continuous power and the system will lose the time and
date if power is lost. When power is restored the clock does not advance. Resetting the clock/calendar is simple but
programmed events may be missed if the clock is not running.
3.6.1 Power Failure Alarm
This problem can be eased by setting the Power Failure Alarm. This feature causes the RFC-1 to call and report
power failures when AC power is restored. The operator that receives the call can reset the clock and calendar and
check the status of devices connected to the RFC-1. For critical applications an uninterruptible power supply is a
better solution.
3.6.2 Uninterruptable Power Supply
With a proper UPS the RFC-1 can operate normally for extended periods without AC power. A small, inexpensive
UPS designed for personal computers will power the RFC-1 for about 1.5 hours. Low end UPS’s are not "instant
switching" but the filter capacitor in the RFC-1 should store enough energy to cover the switching time.
3.6.3 AC Failure Detection on Battery Backup
When the RFC-1 is powered by a UPS or other constant supply, it is possible to monitor AC power line voltage and
generate an alarm when power fails. Simply connect an unregulated DC wall-plug power supply (approximately 3-6
VDC) to one of the telemetry inputs. The telemetry channel can be calibrated directly in volts and set up with a scale
and decimal point to reflect 120 VAC wall current. The Advanced Programming section of the RFC-1 documentation
provides details on setting the telemetry scale and decimal point.
3.7 Lightning Protection Tips
In most installations the RFC-1 is connected to both a telephone line and a tower (via the transmitter). Any
equipment in this situation is subject to severe abuse from lightning. In some installations this happens frequently.
Lightning can enter through the phone line, mistreat the RFC-1 and exit to the station ground system. It can also hit
the tower, elevate the entire ground system above ground by several kilovolts and exit through RFC-1 to ground.
This is called a "ground surge." In other words, the telephone line can hit the RFC-1 or the RFC-1 can hit the
telephone line. The same thing can happen with the power line.
3.7.1 Proper Ground System
The first step in any protection scheme is to install and maintain a high quality ground system. This will serve two
purposes. First, the intensity of the ground surge will be lowered because of the lower resistance to earth ground and
second, if everything is tied together with low impedance conductors, all equipment will stay closer to the same
electrical potential when the system ground takes a hit. All protection devices, equipment racks and transmitters
should be tied together with low impedance conductors, preferably copper strap, as short and as free from bends as
possible. Do not depend on metal conduit for ground connections. A properly designed and installed ground system
will pay for itself many times over in the damage it prevents.