REI Stereo Amplifier CMA 100 User Guide

CMA-100  
Counter Measures Amplifier  
Owner’s Guide  
Research Electronics International  
455 Security Place  
Algood, TN 38506  
931-537-3359  
 
INTRODUCTION:  
REI  
Thank you for purchasing the CMA-100 Countermeasures Amplifier. When doing a  
Counter-surveillance investigation, it is important to analyze all of the wiring in the  
environment to ensure that building wiring is not being utilized to transport audio or  
video information. This wiring may include but is not limited to AC power lines,  
telephone wiring, LAN wiring, security system or access control wiring, intercom  
speaker wiring, heating and cooling wiring, etc… The main reason for analyzing suspect  
wiring is that a microphone that is well shielded is very difficult to detect with an  
ORION. Also, an OSCOR will not detect a hard-wired microphone because there is no  
radiated signal. The CMA-100 is an ideal tool to analyze miscellaneous wiring for audio  
content. Some scenarios of problems that can be discovered with a CMA are:  
1. Utilizing an unused pair of telephone wires or LAN wiring to connect directly to a  
shielded microphone in the suspect environment  
2. A phone set with a hot microphone or hot earpiece used as a microphone.  
3. Microphones can easily be installed in miscellaneous wiring such as thermostats,  
motion detectors, Intercom speakers, AC Junction boxes, etc…  
4. Many digital phone systems have audio leakage that occurs on the digital lines  
due to cross talk within the phone set. A CMA can be used to expose this type of  
vulnerability.  
The CMA-100 can be connected to wiring (assuming that the AC voltage does not exceed  
40 VAC or 250 VDC) and the audio content can be accessed. Furthermore, if there is  
video content on the wiring, the video synchronization pulses can be heard and identified  
through the CMA.  
The CMA-100 is a high gain audio amplifier that is used to detect and identify certain  
types of surveillance devices connected to building wiring including telephone wiring,  
LAN, Server systems, de-energized AC power, etc....  
This multi-functional amplifier has a built in AC/DC digital voltmeter, selectable audio  
filters, and an extremely wide dynamic range.  
Balanced and unbalanced high impedance input provides connectivity to a wide variety  
of suspect wiring.  
The CMA-100 also provides a bias voltage adjustable between –14.5V to +14.5V DC  
that is used to possible activate devices that are voltage or current sensitive.  
All of these functions employ a sophisticated automatic gain control circuitry that is  
unmatched by any other audio amplifier.  
This instruction manual covers the operation and specifications of the CMA-100.  
 
PRECAUTIONS:  
REI  
1. Although the maximum input voltage rating indicates that connection to power  
lines would not be detrimental to the equipment or user, it is NOT recommend  
maintaining connection to such circuits. Extreme care should be taken when  
connecting the CMA-100 to an unknown electrical source. Always check line  
voltage with a multimeter first to determine the risk.  
2. Although the maximum input voltage is 250 volts, the meter will only be able  
to read 199.9 volts.  
 
CONTROLS:  
REI  
Figure 1  
1. On/Low Battery Indicator  
2. Power Switch  
8. Input Attenuator Indicator  
9. Line Bias Indicator  
3. Filter Selector  
10. Line Bias Switch  
4. Gain Selector  
11. Line Bias Voltage Adjust  
12. Headphone Gain  
13. Headphone Jack - 3.5mm  
5. Test Lead Cable Connector  
6. Line Out Jack - 3.5mm  
7. Meter  
 
CONTROLS:  
REI  
IDENTIFICATION  
Please refer to Figure 1 for the following function descriptions.  
1. The Power On Indicator is used to identify when the unit is turned on. If the battery  
voltage falls below 6.9V, then the LED will extinguish and the battery should be  
replaced.  
2. The Power Switch turns the unit on and off.  
3. The Filter Selector is a 4 position rotary switch, provides different options of filtering  
the input audio signal.  
A. Flat - Does not filter the input signal, providing a full bandwidth inspection  
between 25 and 44kHz.  
B. Bandpass - Combines the Lowpass and Highpass in series to create a 3dB  
bandpass from 320Hz to 3.2kHz.  
C. Low Pass - Allows the passage of frequencies below 3.2kHz and attenuation of  
higher frequencies. The effect of this filter is to remove high frequency noise such  
as machinery noise, etc…  
D. High Pass - Allows the passage of frequencies above 320Hz and attenuation of  
lower frequencies. The effect of this filter is to remove low frequency noise such  
as AC power line noise.  
4. The Gain Selector gives the user two operation modes.  
A. Auto - This is automatic gain control (AGC) provides up to 105dB of gain. The  
AGC circuit increases the gain during low input signal conditions and decreases  
the gain for high input signal conditions. This circuit adapts to provide a proper  
audio listening level regardless of the change in input audio level.  
B. Manual  
1.) Fixed gain setting of 0(unity), 25, 50, 75, and 100dB.  
2.) Useful for situations where signal level has large dynamic range that the user  
wants to utilize.  
C. In either case, the Input Attenuator will automatically initiate if the input level  
exceeds 300 millivolts peak-peak. This will provide up to 30dB of attenuation.  
5. The Test Lead Cable Connector is a three-pin keyed connector that insures proper  
polarity of the test leads.  
6. The Line Out Jack provides a signal out, controlled by the "Headphone Gain ", and  
has an output impedance of 600 ohms.  
 
CONTROLS:  
REI  
7. When the Line Bias Generator is turned off, the voltage meter can measure both AC  
and DC volts (Note: AC volts are read as RMS values).  
Note: When the Line Bias Generator is turned on, the voltage meter will measure a  
combination of the voltage in the circuit that the test leads are connected to and the  
voltage presented from the Bias Generator. To read only the Bias Generator, remove  
the Test Leads from any circuit.  
8. The red colored Input Attenuation Indicator will indicate that the input signal is of  
sufficiently high level to automatically initiate the input attenuation circuit. This  
important function provides attenuation to a high power audio signal so that the gain  
circuit will not distort the signal. This automatic attenuator circuit provides  
attenuation for audio levels between 300 millivolts and 31 volts. For signals that  
exceed 31volts peak-to-peak, distortion will occur.  
9. A yellow Line Bias Indicator will indicate the Bias Generator is turned on.  
10. The Line Bias Switch will turn the Bias Generator on or off.  
11. The Line Bias Voltage Adjust will control the magnitude of the bias voltage. The  
mid-position will generate 0V. Turn to the left to generate a negative voltage and  
turn to the right to generate a positive voltage. This function is provided specifically  
to provide DC voltage to power a potential threat such as an electret microphone or  
wiretap device that may be connected to a line. By activating a potential threat, it is  
much easier to identify.  
12. The Headphone Gain is a volume level control for both the Headphones and the Line  
Out. This level control provides up to 15 dB of additional gain.  
13. The Headphone Jack is for use with the included headphones.  
USING THE CMA:  
REI  
Testing for Voltage levels  
Unknown wiring should first be evaluated using a voltmeter to ensure that the voltage  
does not exceed the ability of the CMA. However, if the wiring is known to be low-  
voltage wiring such as Telephone, LAN system, or security system wiring, then the CMA  
can be connected directly to the wiring using the CMA test leads and voltage levels will  
be displayed directly on the CMA.  
 
USING THE CMA:  
REI  
Single Line and Balanced Line Connections  
The CMA provides for connections to either single line systems (typically a single line  
with a ground such as coax) or a balanced pair line such as telephone or LAN wiring.  
For Single Line systems:  
Connect the Green grounding connector to the Black connector.  
Connect the Black connector to wiring ground.  
Connect the Red connector to the single line to be tested.  
For Balanced Pair systems:  
Connect the Green grounding connector to earth ground if available (if not  
available, do not connect to anything).  
Connect the Black connect one of the wires to be tested.  
Connect the Red connector to the other wire to be tested.  
Signal Power Levels  
Signal power levels may vary dramatically. The CMA has two systems that allow the unit  
to respond automatically to a wide range of audio levels. The automatic input attenuator  
prevents gain distortion for situations when the input voltage levels exceed 0.3 volts.  
But, more importantly the Automatic Gain Control Function has a dynamic range of  
105dB. In basic terms, this means that that the unit can automatically adjust to audio  
signals ranging from 2 microvolts to 0.3 volts.  
Strong Signal Interference  
If the input is attached to an AC voltage greater than 40 volts, the audio content will be  
masked.  
Signal Frequency Interference  
Wiring in a building is very susceptible to interference from ambient electromagnetic  
noise sources. The most common type of audio interference is from the AC power lines.  
This noise is typically either 50 or 60Hz fundamental frequency; however, there are  
harmonic frequency components that also cause interference at 100/120Hz, 150/180Hz,  
and possible up to 200/240Hz. For this reason, the CMA has a built-in High Pass filter  
that filters out audio noise below 320Hz.  
Also, high frequency electromagnetic noise can interfere with audio signals. This type of  
higher frequency noise can be generated from industrial machinery, computers, fax  
machines, and digital phone systems. Hence, the CMA has a built-in High Pass filter that  
filters out audio noise above 3,200Hz.  
Providing DC Bias  
It is a common practice to utilize electret type microphones for audio surveillance, and  
electret microphones require a voltage supply in order to function. Therefore, when  
evaluating suspect wiring, if the wiring does not have any voltage on the line, it is  
recommended to apply a DC bias voltage to activate any potential microphones. The DC  
Bias Voltage should only be used after ensuring that the line does not have an active  
 
USING THE CMA:  
REI  
voltage supply. Then, the DC Bias voltage can be switched on and the control knob  
slowly turned to both negative and positive directions while listening with the  
headphones to see if a microphone is activated.  
Using the CMA with other probes  
The CMA can be connected to a variety of other probes.  
Inductive coil - for coupling to an audio signal without making a metallic  
connection.  
Contact microphone - for detecting sound within physical structures.  
Over voltage protection  
If the CMA's input voltage limit is exceeded, then damage will most likely occur that will  
make the CMA require repairs. The CMA case is isolated from an input up to 500V.  
Therefore, if the input is allowed to exceed 500 volts then a shock hazard will exist.  
Over current protection  
When connected to an AC power line, the BIAS GENERATOR should not be activated.  
In the event that it is, there are input current limiting devices that will protect the delicate  
parts of the CMA. After disconnecting the input, it will take several seconds for the  
CMA to work properly again.  
 
SPECIFICATIONS  
REI  
INPUT IMPEDANCE:  
50k ohm balanced  
>75 dB  
COMMON MODE REJECTION:  
MAXIMUM USABLE INPUT:  
PREAMP AUTO ATTENUATOR:  
DYNAMIC RANGE:  
31 Vp-p  
0 to –40 dB (with Input Atten LED)  
145 dB min.  
MANUAL GAIN CONTROL:  
HEADPHONE GAIN CONTROL:  
MAXIMUM SYSTEM GAIN:  
FREQUENCY RESPONSE:  
HIGH PASS FILTER:  
0,25,50,75,100 dB  
0 to 15 dB  
115 dB  
25 Hz to 44 kHz  
320 Hz to 44 kHz  
25 Hz to 3.2 kHz  
320 Hz to 3.2 kHz  
16 ohm, 105dB SPL limited  
600 ohm  
LOW PASS FILTER:  
BAND PASS FILTER:  
HEADPHONE AUDIO OUTPUT:  
LINEOUT AUDIO OUTPUT:  
BIAS CONTROL:  
0 to +/-14.5 VDC, 5 mA max (Over current protected,  
input Impedance is reduced to 3.6k ohms when bias is  
active)  
DIGITAL VOLTMETER:  
POWER ON/LOW BATTERY LED  
BATTERY:  
3.5 digit, auto zero, auto polarity, +/-199.9V AC or DC  
LED off @ 6.9V  
9 V ALKALINE (5-30 Hrs typical run time)  
250 AC/DC  
MAXIMUM INPUT VOLTAGE:  
LEAKAGE RESISTANCE TO CASE: >10M ohms  
SIZE:  
7.3” (185.4mm) x 2.75” (69.8mm) x 1.75” (44.5 mm)  
WEIGHT:  
12.1-oz (343g)  
 
 
 

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