Data Delivery Devices RFScada 2DI-4DO Long Range Spread Spectrum Bi-Directional Wireless Telemetry Unit User Manual

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 21 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
VSD / VFD Control. 
 
A variable speed drive may be controlled at a distance using the RFScada units. Depending on the type 
of drive, the speed may be raised or lowered and other features may be operated. The RFScada units 
provide automatic shutdown in the case of any system or communication failures. 
 
 
 
  
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 22 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
Access Control / Monitoring 
Here a pair of wireless RFScada units remotely protect, monitor and control access to a secure location 
up to 20 miles away. Alarms are activated whenever access is required or gained. The electrical lock may 
be controlled remotely as well as locally. Remote indication is supplied to show if the door is securely 
closed, when it is opened plus full visual status of conditions. Alarms indicate all faults and abnormal 
conditions, such as power fail or forced entry.  
 
     
 
  
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 23 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
Security / Environmental Systems 
From up to 20 miles, without interconnecting wires the RFScada units can control and continuously 
monitor environmental systems such as pumps, fountains, heaters and security devices. Alarms are 
activated to indicate any fault conditions, and battery backup provides full operation during power failures.   
 
  
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 24 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
External Antennas. 
In some situations, due to distance, obstacles or other factors an external 
antenna may need to be installed on one or possibly both units. If in doubt two antennas 
may be ordered, then one returned for credit if not required. Two FCC approved Yagi 
type antennas (9 dB and 12 dB gain) are offered for operation with the device.  
Also supplied with the antenna is a suitable cable, with a special ‘reverse polarity’ 
SMA plug to attach to the antenna connector on the RFScada board. At the other end of 
the cable is a weatherproof ‘N’ type connector that connects to the antenna. A 
weatherproof cable entry clamp is also installed on the cable, so it may be mounted in a 
suitable hole drilled in the case. The length of cable needs to be specified when 
ordering, bear in mind that signal loss due to the cable will be approximately 1.5 dB per 
10 feet, so limit the cable length to the minimum required. The total installed cost of 
antennas including the cable, pole (if needed), time and labor required etc. is often not 
significant between the 9 dB and 12 dB antennas, so generally the higher gain antenna 
is recommended. There is also a better chance that the higher gain antenna will give 
satisfactory performance without requiring an external antenna on the other unit. 
An excellent source of technical information concerning the antennas, radiation 
patterns, selection criteria, features etc. may be found online at 
http://www.astronantennas.com/framed_library.html
 
 
             
   
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 25 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328   
FCC RF Exposure Warning 
In order to comply with the FCC RF exposure 
requirements the RFScada unit may only be used 
with approved antennas that have been tested with 
it. A minimum separation distance of 20cm must be 
maintained from the antenna to any nearby 
persons. The RFScada unit is not classified as a 
portable device per FCC Section 2.1093  
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 26 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
Sample Questions and Applications. 
 
900 MHz vs 2.4 GHz  
It seems that everywhere you look another ‘spread spectrum’ 2.4GHz devices comes 
out, including cordless phones, local wireless computer networks for homes and offices, 
video cameras, video links etc. Isn’t the very popular 2.4GHz frequency band the way to 
go, a quick survey shows almost everything wireless in Wal-Mart’s electronics 
department to be a 2.4 GHz device.  
 
For a long range, high reliability product such as the RFScada device the 2.4 GHz band 
is not the best choice. For short range (typically less than a hundred feet), generally 
indoor, high bandwidth devices such as video links or wireless computer networks the 
2.4 GHz band has some advantages, such as using a smaller antenna than required by 
900 MHz devices. Many public places like airline terminals, hotels, hospitals, coffee 
houses, bookstores etc. are installing these wireless networks, and so the band has 
quickly become saturated with these devices, especially in urban locations. This often 
results in interference and poor (or no) operation for devices that compete in this 
frequency range; many users are now finding that additional 2.4GHz devices will not 
operate satisfactorily in the vicinity of other 2.4 GHz devices. An additional advantage of 
the 900 MHz band is the greater range (typically 3 times that of 2.4GHz) and reduced 
attenuation from rain when compared to 2.4GHz devices. The 900 MHz band is the best 
choice for devices such as the RFScada products, which are designed for the highest 
reliability, interference rejection and longest range in hostile environments.  
  
Cordless Phone 
I have a ‘spread spectrum’ cordless phone at the house, it has trouble operating more 
than 100 feet from the base station and it certainly does not work ¼ mile away. I 
understand that the RFScada is also a ‘spread spectrum’ device, how can it operate 1, 5 
or even 20 miles away? 
The main reason is power. The term ‘spread spectrum’ covers a general method of 
transmission, where transmit and receive frequencies are constantly changing or 
‘hopping’ through various channels. This method was devised as a means to allow 
many devices to effectively share a bandwidth. There are several classifications allowed 
by the FCC to cover different devices and applications, these classifications also govern 
both the RF power and antenna systems that may be used. These classifications all use 
the generic term ’spread spectrum’ as a transmission method. The FCC designates 
your cordless phone and similar consumer devices as a ‘portable device’ with a severely 
limited RF power output and antenna. The RFScada is not designated in this group, and 
therefore may transmit both with a higher power plus it may also use an FCC approved 
directional antenna that provides more system power gain in certain directions. In fact, 
because of the higher RF power output emitted by the RFScada unit the FCC mandates 
that it must maintain a separation distance of at least 20 cm (about 8 inches) to any 
nearby persons. 
 
True Range 
The range is mentioned as 0.25, 5 and 20 miles etc. What is the real range? 
This is a very difficult question to answer, since it will vary in every installation. The 
actual range will depend on many factors, including the device location, height, shape of  
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 27 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
the terrain, terrain surface, obstacles, the antenna used, proximity to similar devices etc. 
As a very general guideline in a typical, outdoor location where each RFScada unit may 
be visible from the other and using the internal antennas supplied with the standard 
product a range of at least two miles is to be expected, and five miles is usually 
possible. A similar ‘line of sight’ installation, using the optional 12 dB gain Yagi antennas 
at each end should produce a range of 25 miles. Using the internal antenna and inside 
a typical factory, with moving and stationary machines, obstacles, metal walls, 
interfering devices and no line of sight the range may be reduced to a few hundred 
yards. If one unit were to be located inside a 2 inch thick lead box then (just like any 
other RF transmitter and receiver) the range will be reduced to zero. The range 
depends on many factors. Please see the product manual for a full discussion of factors 
that may affect the range. If you are unsure of the performance for your application 
please inquire about the availability of evaluation units for testing at your location.     
 
Separate Transmitter and Receiver. 
I ordered a transmitter for my tank and receiver for the well control. There appears to 
have been a mistake as both units look to be identical. Shouldn’t one be a transmitter 
and one a receiver?  
They are identical; each unit is both a transmitter and a receiver. This is the only 
way that units are able to positively verify correct operation of the other unit. Whatever 
the states of the ‘input contacts’ are at one unit will be reflected at the ‘output contacts’ 
states at the other unit. The units continually communicate with each other to ensure 
constant and valid data exchange. If for some reason a unit needs to be replaced (for 
instance it may be been damaged or stolen) then another standard unit may replace it. 
  
System Data Verification 
How do I know that the output data I receive is valid and is not interference from another 
device?  
There are many levels of sophisticated data encryption and protection incorporated 
in the device. Lets follow a typical signal to see what actually happens. First of all the 
‘input data’ (input contacts) at the transmitter must be stable for a minimum period of 
time before the signal is processed. This can be seen by the brief (approx. quarter 
second) ‘de-bounce’ time delay between the input signal changing state and the 
transmitting data ‘input status’ indicator LED reflecting the change. This delay allows the 
input signal to stabilize, removes any spurious noise that may be on the input signal and 
it prevents possible relay ‘chatter’ at the other unit due to an intermittent input signal. 
Once the input signal is stable it is encrypted in a data format that incorporates a 
constantly changing rolling code and is then mixed with other data pertinent to the unit, 
such as the local AC power status. A 16-bit cyclic redundancy check (CRC) value is 
then calculated for this coded data and added. Now the encrypted plus CRC coded data 
is passed to the RF section and transmitted using 25 constantly changing frequencies 
and using yet another, completely independent 16-bit CRC with a different algorithm 
from the first.  
The remote unit receives the RF data and verifies that the 16-bit RF CRC is correct. 
It then further analyzes the received data and verifies that it also passes the second 
CRC encryption check. The transmitted ‘input data’ plus other information from the first 
unit is then removed from this dual-verified data. Finally this data is used to update the 
state of the outputs, to faithfully reflect the input state of the first unit. Any ‘single bit’ 
error in the whole process will result in an unverified data packet, and that data will be  
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 28 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
completely ignored. If ‘correct and double verified’ data does not arrive at a receiver for 
about 2 seconds the unit will extinguish the ‘COMMS OK’ status LED and set the 
‘COMMS OK’ relay output to inactive, ie its normally open contacts will open. If ‘correct 
and double verified’ data does not arrive at a receiver for about 5 seconds all the 
outputs will change to the default output state, where each output relay will revert to the 
‘inactive state’, in other words the normally closed contacts will become closed and the 
normally open contacts will open. After good data has been received at one unit it will 
repeat the whole process by transmitting its own input states to the other unit in a 
similar manner. Each unit will complete the whole cycle (input/encrypt, transmit data, 
receive data, decrypt, update outputs) several times a second to insure that the output 
data is valid. If either unit fails for any reason the maximum time before all outputs 
change (on both units) to the ‘default’ state will be 5 seconds.       
 
Failures or Damage to the System. 
What happens if one box fails or is vandalized?. 
If either unit fails or communication is disrupted for any reason the maximum time 
before the outputs change to the ‘default’ state will be 5 seconds. The outputs on both 
units will change to the default state, regardless of which unit failed. 
 
Functional Integrity and Verification 
We want to replace some competitors units that have poor range and marginal 
performance. Also, since we now realize the competitors units we own are just ‘one 
way’ devices we have actually been using two complete sets of them for each signal 
monitored, as we need to verify that they are actually functioning - data integrity is very 
important for this application. With the RFScada units is there a way to tell if the remote 
unit is receiving my signal correctly? 
Yes, there is full data verification. Unlike competitors ‘one way’ or ‘report on an 
event’ type these maintain continuous communication and are fully bi-directional so 
there are several ways to verify full and correct data transfer. Since both units are 
identical with built in transmitters and receivers it is easy to verify reception of data 
remotely. First of all, by the very nature of the device if the two on board transmit and 
receive status LED’s are quickly flashing (normal operation) the devices are both 
exchanging good, verified data. Secondly, the normally open, ‘Communication OK’ 
contacts (connector J5 pins 3 and 4) will be closed all the time that the devices are 
maintaining a verified data exchange; and the ‘COMMS OK’ status LED will also be 
illuminated. When communication is interrupted, at either unit and for any reason the 
‘COMMS OK’ contacts will open plus the status LED will extinguish at both units within 3 
seconds of the interruption. Finally, if required it is possible to manually verify complete 
operation of both units. Take the second, unused output of the remote unit and directly 
connect it to an unused input (for example input two) on the remote unit. At the ‘base’ 
unit close (short together) input two. This will cause output two of the remote unit to 
close, which is now directly wired to input two on the remote unit. This state of input two 
will now be transmitted back to the ‘base’ unit by the remote. Therefore, providing both 
units are functioning and communicating changing the state of the ‘base’ unit input two 
will cause the monitored output two at the base unit to also change, all within a second. 
This verifies, in order, full local data input, encryption, local RF transmission, remote RF 
reception, remote decryption, remote output, remote input, remote encryption, remote 
RF transmission, local RF reception, local decryption, local verification and local output 
all within a second.       
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 29 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
 
AC Power Loss and Generator Operation 
Our remote unit is powered from a generator that automatically starts and runs for a 
couple of hours then stops for a few minutes. The remote unit is successfully monitoring 
the tank level, and continues to operate correctly when the generator is stopped, 
powered by its internal rechargeable battery. Is it possible to also monitor when the 
generator is running? 
Yes, this capability is built in. The normally open contacts of ‘Remote AC OK’ output 
(connector J4 pins 1 and 2) continually indicate the status of the remote units AC power. 
When the generator is running at the remote unit it will transmit this status to the ‘base’ 
unit and it in turn will activate (close) the ‘Remote AC OK’ contacts; the status LED will 
also be illuminated. It will become inactive and the LED will be extinguished when the 
generator (or other AC power source) stops.   
        
Interference between Multiple Units 
We have a pair of RFScada units that have been operating flawlessly for some time. We 
now need another pair but they will be located within a couple of miles from the first. Will 
two pairs of RFScada interfere with each other? 
Each pair of units is matched together for transmission and reception. There are 
seven sets of identity that the units may have, so up to seven pairs of units may all 
operate in close proximity so long as they all have different id’s. When supplied the 
standard units are configured for set ‘A’, but they can be configured at the factory for ‘A’ 
to ‘G’. A record is kept of the units supplied for each customer, so when ordering 
additional units please advise if you need a replacement for a damaged one or a unit to 
operate on a different frequency set. There are solutions offered for applications where 
more than seven pairs are required to operate, or systems where there is a single ‘base’ 
master unit and multiple slave units, please consult the factory for further details.  
 
Rain Attenuation 
Here in the jungle we often experience heavy rain. Does it affect operational range? 
Heavy rain does have an affect on the range, but it is generally negligible. It 
attenuates the signal by approximately 0.2dB per mile for a torrential storm, which 
means a range difference of less than a few feet per mile. 
 
Pampered Horses 
We train and stable many valuable horses for clients on a large ranch. For security 
reasons we have just installed an electrically operated locking gate restricting access to 
the property. The gate is powered by a solar panel and 12 Volt battery since it is remote 
from any source of power. It also came with remote controls from the manufacturer that 
allow us to operate it from our vehicles when we are within 50 feet or so, but they will 
not operate from our main office which although visible from the gate is almost a mile 
away. We have considered purchasing additional remotes for staff to use, but we also 
have many frequent visitors and deliveries. If the gate is not staffed we install a sign that 
advises visitors to sound their horn on arrival, whoever is closest drives down by the 
gate and opens it. This most undignified entry method is obviously not acceptable for 
us, our clients or the horses that may be startled by the noise. The gate opener has a 
provision for a manual switch to allow anyone to operate the gate, but we have not 
installed that since it defeats the purpose of having the gate for security. The only other 
option available is a keypad by the gate with a code to enter, but again it is not suitable  
						

							RFScada User Manual Version 1.7 Copyright ©2002 Data Delivery Devices LLC   Page - 30 – 120 NE DeBell Suite B Bartlesville OK 74006      Tel 918-335-3318      FAX 918-335-3328 
for our many visitors. We would also like to be alerted when the gate is operated so we 
may monitor activity. The gate installation companies we have contacted all have just 
one possible solution left for us - digging a trench for over a mile around the lake and 
across the beautifully landscaped grounds, then installing a cable connected to the gate 
switch; allowing us to operate the gate from the office. This ‘solution’ would be very 
disruptive to our operations, very expensive, we would not know when vehicles with 
remotes came or left and our clients would still be sitting in their vehicles honking the 
horn to gain entry. Can the RFScada solve any of these problems? 
Yes, the RFScada can solve all of your problems. Here is how to do it. Install one 
unit at the office powered by the standard AC line. Connect a normally open push 
button switch to ‘input one’, this will be used to allow gate operation from the office. 
Connect an indicator light or alarm indicator such as a bell wired to use the ‘output one’ 
normally open contacts. Install the other (we will call it gate unit) by the gate control. 
The gate unit may be powered directly from the 12 volts DC supplied by the gate control 
battery and solar panel since its current draw is small. Connect the normally open 
contacts from ‘output one’ to the ‘manual operation’ switch input on the gate control. 
When the push button is pressed in the office the gate will operate. Now to solve the 
next problem, alerting office personnel when a guest arrives. A switch may be installed 
by the gate connected to ‘input one’ on the gate unit. When visitors arrive they may 
press this button, which in turn will activate the alarm at the office. When the office 
personnel have verified the guest’s identity they may operate the gate from the office. 
Rather than having guests press a button by the gate another option is to use a 
motion/proximity detector or ‘breaking beam’ type detector ahead of the gate connected 
to ‘input one’. This detector could be situated a short distance before the gate to provide 
an alarm at the office before the guest arrived, minimizing any delay. As an added 
measure of security the second unused input to the gate unit may be wired closed, or 
even better connected to a tamper switch or a switch active when the gate was 
positively locked. Due to this the office unit would have ‘output two’ active all the time 
under normal circumstances, so another alarm (or it could be wired in parallel with the 
first alarm) would be connected to the ‘output two’ normally closed contacts. If the 
secure, continuous data communication between the office and gate units were 
disrupted for any reason, including the gate battery failing, cut wires, theft, vandalism 
etc. then ‘output two’ at the office would change state alerting the office personnel. The 
RFScada provides a complete, secure and cost effective solution that adds additional 
benefits without requiring extensive digging, disgruntled clients or frightened horses.             
 
Medical Applications 
We have some medical equipment that may be able to utilize two RFScada units. Are 
they suitable for this for application?  
No, they are not. The RFScada units are not authorized nor intended for life support 
or medical applications. 
 
FCC License 
Our old SCADA system radio modem & RTU combination has failed again and we 
would like to replace it with two RFScada units. Do we need to convert our present FCC 
license to use the RFScada devices?. 
No need. No license is required to own or operate the RFScada devices within the 
USA, and the FCC already approves them. Save the renewal fees and throw away your 
old FCC license along with the failed SCADA system.