Note: ACSS is in the process of forming and is not yet an established trade association. At present ACSS is fully owned and operated by Norbert Zaenglein as a sole proprietorship

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(Terminology Courtesy Tim Johnson)

A

Access Area - The area of vulnerability to intercept between a telephone subscriber and the serving central office.

Acoustic Patch - The placement of a microphone near a loudspeaker or earphone as a means of coupling sound between two audio equipment lines. Sometimes used to attain an impedance match when no other means are available.

Agent Transmitter - A small radio transmitter concealed on a person's body for agent or informer protection or consenting monitoring.

Amplifier - An electrical circuit that makes a small signal larger by increasing the strength (amplitude) of the carrier.

 Amplitude Modulation - A method of impressing audio signals on a radio carrier signal by varying the strength (amplitude) of the signal.

Antenna - A conductor or system of conduction for transmitting or receiving radio signals.

Antisidetone Circuit - Circuit in a telephone used to reduce the volume or sound heard in the receiver (earpiece) that has been picked up by the transmitter (mouthpiece) of the same telephone. (See sidetone)

Appearance Points - A location where physical or electrical access is readily available to a given telephone line pair.

Audio - Sound waves audible to the human ear.

Audio Loop - A system using a single or a few turns of wire run completely around a room and connected to the speaker terminals of a power amplifier to excite inductive pickup headsets and thus achieve cordless operation.

B     

Backstrap - The connection of a telephone spare or leased pair to a subscriber pair at some appearance of the latter as a means of carrying the intercepted signal to a listening post.

Band Splitting - A process used in some simple voice scrambler devices in which voice frequencies are separated by filters into several frequency band ranges so that each such band can be "scrambled" separately.

Bandwidth - A specification describing the highest and lowest frequencies an amplifier can handle with no loss beyond that stipulated.

Barrel Effect - A trick of echo in a small chamber which causes distortion of a sound similar to that experienced by talking with one's head in a barrel.

Battery - A group of individual electrical cells.

Block Wiring or Block Cable - Wiring or cable on the outside of a building or buildings. This cable or wiring is thought of as being confined to a particular (city) block and not crossing a street or alley where it would be exposed to possible contact with electrical service conductors. It is not thought of as being exposed electrically as it is on the building. Substation wiring, under these conditions, does not require protection from high voltage.

Blue Box - An illegal device used mainly by phone phreaks to gain entry to operator circuits from a subscriber phone line. The device emits a tone which is used by the phone company to activate toll -free circuits for operator use.

Breakdown Voltage - A voltage at which a semiconductor device will conduct in the reverse polarity.

Broad Band - In amplifiers, capable of handling a wide range of audio or radio frequencies. In transmitters and receivers, able to deviate + and - 75 KHz from the FM carrier frequency and thus able to accommodate high fidelity music.

Bug - A clandestine listening device; generally a small, hidden microphone and radio transmitter.

Bugging - The process of monitoring conversations by electronic means.

Bypass - The alteration of a telephone instrument or intercom system so that it will pass audio even in the on hook or deactivated position. (In telephones, an alteration to the hookswitch.)

C

Capacitor - An electronic component which blocks the passage of DC while allowing the passage of AC. In telephones, a capacitor is used to block the direct current of the line from flowing through the ringer coils

Carbon Microphone - A microphone which depends for its operation upon variations in resistance of carbon granules which change in applied pressure from the diaphragm, and require a battery or external power source for its operation.

Carrier - A term broadly used to designate a single RF frequency upon which audio signals can be impressed.

Carrier Detector - A countermeasures receiver used to detect the presence of line carrier signal on a wire pair.

CCTV - Closed Circuit Television.

Center of Conversation - An imaginary point midway between conversationalist. A point for potential microphone placement.

Central Office - The main telephone equipment housing exchange or the switching center for a specific geographical area.

Ceramic Microphone - An inexpensive pizoelectric microphone which is more rugged than a crystal microphone, but which delivers a slightly weaker signal from the same acoustical point.

Cheesebox - An adaptation of a telephone answering device used to interconnect two telephone lines run to the same premises and enable a caller to the first phone seemingly to answer a call made to the second. The device gives the user the capability of direct distance dialing to receive expected calls due at a specific time without being charged for a completed toll call and without letting the other party 79 know his actual location.

Ciphony - A technique by which mechanical and/or electrical equipment is used for coding and decoding voice messages. It is more secure and more costly than simple scrambling and requires digitizing of the speech prior to code processing.

Cocktail Party Effect - The ability of the human brain to interpret differences between the sounds heard in the right and left ears as to be able to listen selectively to sounds emenating from any selected point in a room. This enables a person to listen exclusively to a single voice from among the general bable of voices at a cocktail party.

Commission, The - The National Commission for the Review of Federal and State Laws Relating to Wiretapping and Electronic Surveillance or Intercept. See Section 804, Public Law 90 -351.

Common Battery - Telephone systems where all power is furnished by a common battery located at central office.

Compression - A bunching up of air particles. Also used to reduce the dynamic volume range of broadcast transmitters, especially for listeners in cars.

Connecting Block - The connecting blocks in the immediate vicinity of a telephone instrument through which the instrument is connected to the system.

Contact Microphone - A microphone, usually crystal, which has no diaphragm of its own and uses some resonant surface, such as a wall, to make its working parts vibrate.

Conversation Discipline - A countermeasures term which refers to the avoidance of making compromising sounds during the conduct of the initial non -alerting radio frequency phase of a TSCM survey.

Correlation - In countermeasures, the hearing, via earphones attached to an item of search equipment, of the same sounds that are being heard "live" in the area under examination. Normally, this is an indication that a surveillance device has been detected.

Countermeasure - The total effort made to protect a potential target against electronic surveillance.

Crosstalk - The intermingling of audio signals between adjacent pairs of wires as in a telephone cable or between adjacent channels in stereo equipment.

Crystal Microphone - A microphone which uses the pizoelectric effect of quartz crystals to generate electrical signals from sound energy. Due to their particular sensitivity to high frequency sound, crystal microphones are generally limited to contact microphone applications.

D

Dead spot - A geographic location in which signals from a given radio transmitter are received poorly or not at all. Dead spots are usually due to phase cancellation.

Decibel : dB - One -tenth of a Bel. A representation of the power ratio between two signals. One dB is the least change in power of sounds the human ear can detect. Three dB represents a power change of 2:1, and 20 dB a power change 100:1. The scale is logarithmic, viz dB = 10 log (for voltage dB = 20 log ).

Dedicated Feeder - A cable which runs directly from a telephone exchange to a servicing area with no 80 access points enroute.

Demodulation - The process of sensing variations in a radio frequency carrier and reconstructing the original modulating intelligence from it. Also called detection.

Deviation - The number of kilohertz above and below the carrier frequency caused by the modulating signal in an FM transmitter.

Device - Any electronic or mechanical apparatus that can be used to intercept oral, visual, or wire communications.

Dial - The control, operated by the user, used to operate the central office equipment so as to obtain the desired connection to another phone.

Dial circuit - The signaling circuit of the telephone on outgoing calls. This circuit, in the sets generally discussed, consist of a device that will open the central office line circuit a certain number of times each digit dialed and at a certain speed, usually about 10 times per second.

Dial Mechanism - Numbered rotating wheel on telephone instruments to generate calling impulses of number dialed. Newer telephones use touch tones for the same purpose.

Diaphragm - Any thin material used in a microphone to vibrate other working parts in response to sounds in the area. The same sort of material is used in a loudspeaker to generate sound waves in response to electrical signals from an amplifier.

Diode - A Semi -conductor or other device which acts as a one way valve for the passage of electric current. Diodes are used to prevent reverse current flow in battery pack assemblies and as rectifiers in a variety of applications.

Directional Microphone - A microphone which responds best to sounds from a particular direction. Normally not desirable for investigative applications.

Director - A parasitic antenna element located in the direction of the major lobe of the radiation pattern for the purpose of increasing either transmitted radiation toward, or received sensitivity from, that direction. An antenna may have several director elements, these are usually slightly shorter than the "dipole" or radiating/reception element connected to the transmitter or receiver by cable. (See also "reflector")

Distortion - A difference in the reproduced sound from that of the original.

Double Demodulation - The process of recovering the intelligence from a subcarrier after the subcarrier has been detected from the original carrier.

Drift - Failure to maintain established frequency by an oscillator either in a transmitter or receiver.

Drop -in Transmitter - A small Wire Communications Intercept (WCI) transmitter built into a microphone portion of a telephone transmitter.

Dynamic Microphone - Any one of several types in which the coil is attached to the diaphragm and surrounded by a magnetic field from a permanent magnet.

E  

Earpiece - A small electro -magnetic speaker for use in a telephone handset. 81

Electret Microphone - A permanently charged condenser microphone which has an extremely low mass diaphragm and is thus substantially less responsive to clothing noise than many other microphones.

Electronic Search - An examination of a specified area in search of Oral Communications Intercept (OCI) and WCI devices. Also called countermeasures search or a "sweep".

F

F.C.C. - Federal Communications Commission.

Facsimile Transmission - A line scan method of transmitting pictures; wirephoto.

Feedback - Any transfer of energy from the output end of an amplifier back to the input or some other earlier stage. In audio circuits, this often results in a loud squealing sound from loudspeakers or in headphones. Feedback may be positive (in phase) or negative (out of phase).

Field Strength Meter - An instrument used to indicate relative measurement of the radiation field close to an operating device.

Find - A discovery of a WCI or OCI device.

Fortuitous Conductor - Any conductor used in a concealed microphone installation which was not specifically installed for that use. Any conductive metal used to replace or supplement a dedicated wire run.

Frequency Modulation - A system of impressing audio signals on to an RF carrier by causing them to make slight alterations in its frequency.

G

Gimmick - A capacitive connection made by simply twisting two insulated wires together. A gimmick is one simple means of coupling the antenna of a surveillance transmitter to a telephone line or some other makeshift extension antenna.

Grass - The clutter which occurs on the panoramic display of a receiver due to noise, etc. So named because of its appearance on standard green cathode ray tube displays.

Ground - A positive side of the central office or other battery. All grounds are to be tied together and connected to a ground rod at the central office. Also refers to protective ground at the substation.

Ground Wire - The conducting lead from a device to an earth ground connection.

H

Half Wave Antenna - Antenna with active elements spanning a distance equal to one half the wavelength of the operating frequency.

Handset - The part of the telephone instrument used for talking and listening.

Handset Cord - Flexible connecting wire between the telephone and the handset. Usually three or four conductor.

Hard Room - A room with hard surfaces and little soft furniture or drapery to inhibit the reflection of sound. Hard rooms tend to develop interfering reflected sounds and require greater attention to acoustical factors of microphone placement in surveillance applications.

Harmonics - A harmonic of a given frequency is any multiple of that frequency. Double a frequency is 82 the second harmonic, triple is the third harmonic.

Hertz - A measurement unit of frequency equal to one cycle per second.

Hidden Space - A philosophy of concealment based on the fact that things which appear solid to the eye are often accepted as being so without further investigation.

Hookswitch - Switch contacts inside the telephone which remove the telephone from the line circuit when the handset is returned to the cradle (hung up).

Hot Pack - An item of countermeasures equipment usually hand fabricated by the using specialist. It contains batteries capable of delivering up to 1200 volts and provisions for determining whether an item under examination is passing current due to a neon or zener bypass.

Hot spot - A physical location where a radio signal is strong due to reflected signals arriving in phase with the direct signal and reinforcing the latter.

I

Image Frequency - A frequency which differs from that of a desired radio signal by twice the IF in a receiver. If the early tuning circuits are wide band enough to let this image frequency pass, it too can generate the same IF and thus cause interference.

Induction Coil - A sensing coil usually associated with the microphone input of a tape recorder and used to pick up audio signals magnetically. The most common application of an induction coil is the familiar telephone pickup coil.

Infinity Transmitter - A transmitter designed for installation inside a telephone instrument. It is not a WCI device, but rather an OCI which can be activated by dialing a target phone and sending a special tone over the line to activate it, normally after the recipient has hung up. The device works even on direct dial long distance calls (at an "infinite" distance). The "harmonica bug" frequently sensationalized in the press is a form of infinity transmitter. The telephone will show busy to incoming callers.

Inside Wire - Telephone wiring inside the user's premises. Minimum of two conductors but includes wiring cables as large as needed. Also referred to as house wiring.

Installation Record - A complete file kept by an investigative unit on each technical surveillance device installed. It includes a copy of the authorizing document , case number, installation plan, installation report, special description of problems encountered, etc.

Intelligibility - The quality, especially tape recorded speech, of being understandable in the sense that each individual word can be heard and recognized by a listener with normal hearing.

Intercept - The aural acquisition of the contents of any wire or oral communication through the use of an electronic, mechanical or other device.

Intermediate Frequency (IF) - In receivers, that frequency to which selected incoming signal is converted by hetrodyning with the local oscillator signal and to which the remaining circuits of the receiver can be precisely tuned regardless of the frequency of the desired incoming frequency.

J

Jamming - The generation of an audio or electronic signal with the intended purpose of over riding or interfering with the signal someone else wishes to receive.

K

Key Telephone - A system located on a subscriber's premises which provides additional switching and signaling features not included in standard residence or commercial service. Mostly used in commercial multi -line installations where one instrument has access to several separate lines.

Key Telephone Unit or KTU - A unit consisting of relays, capacitors and resistors as necessary to perform certain functions in a key telephone system.

Key Telephone System or KTS - A complete key telephone system, either in operation or in a package ready to be installed.

L

Law of Inverse Square - A law expressing the fact that the power of radiated energy decreases in proportion to the square of the distance from the source.

Leased Line - Dedicated line leased to customer for specific communications use.

Line - Usually thought of as a pair of wires from the telephone to the central office. This would include the inside wire, the drop wire, cable pair, cross connection at the central office and all terminations of this pair of wires.

Line Carrier Receiver - A receiver used to detect unradiated radio signals on a power line or other conductor.

Line Carrier Transmitter - A transmitter designed to send an RF signal down a wire rather than radiating them into space from an antenna.

Line Driver - An amplifier situated near a microphone but powered from the remote end of a wire link. Its purpose is to strengthen the microphone signal before electrical noise on the line is added so that a better S/N ratio will exist at the receiving end of the system.

Line Input - The jack on a tape recorder designed to accept strong signals such as from a WCI or a radio receiver.

Line Pair - Two related wires, working together. Usually used with reference to telephone circuits.

Listening Post - The site at which radio signals are received or wired microphone lines terminated for the purpose of monitoring and/or recording intercepted communications.

Local Oscillator - An oscillator used to produce a sum or difference frequency which will hetrodyne with a desired incoming signal frequency to produce the intermediate frequency of a radio receiver.

M

Magnetic Field - The invisible lines of force which surround a magnetic object. The space in which these lines of force exist.

Magnetic Microphone - A microphone which uses vibrations in the reluctance of a magnetic circuit as its operating principle.

Microphone - A device (transducer) used to change sound waves into a fluctuating electrical current.

Microphone Input - The jack on a tape recorder or amplifier designed to accept weak signals from a microphone or induction coil. The signal fed into such a jack.

Mobile Listening Post - A listening post established in a car, van or other movable conveyance. 84

Modulation - The process by which audio signals are impressed on an RF carrier.

Mounting Cord - In telephone systems, the cord between the telephone and the associated connecting block.

Multipath - The virtually infinite variety of reflective routes radio waves may travel (depending on frequency and propogation qualities) to reach any given point. Their collective arrival in or out of phase may determine a "hot spot" or "dead spot".

N

Narrow Band FM - FM radio which deviates no more than + or - 5 KHz as a result of modulation.

Neon Bulb - A device consisting of two conductors enclosed in a neon gas inside a glass bulb. It requires a low voltage, (usually between 50 and 100 volts) to fire the gas. Once fired, the neon lamp will conduct AC or DC.

O

Observation Post (OP) - A surveillance point from which an investigator can view a particular target area.

On Hook - In telephone systems, an instrument with the handset hung up.

Oral Communication Intercept (OCI) - In public Law 90 -351, the acquisition by ear of any spoken communication through the use of any electronic, mechanical or other device.

Oscillator - An electronic device which generates alternating current signals.

Outside Plant - Any and all telephone equipment located outside of the central office. Includes the underground cables, poles And aerial cables, drop wire, and equipment installed at the user's premises.

P

Panoramic Display - A device designed to display all signals present in a given frequency band as vertical pulses on a horizontal trace.

Parabolic Microphone - A microphone with a large disk -like attachment used for listening to sounds from a great distance.

Parallel Radio Tap - Radio frequency tap transmitter which is attached across both wires of a telephone.

Parasitic - Tasking operating power from the supply meant for one device and using it for another. Also used for antenna elements such as reflectors and directors.

Pen Register - An instrument that records telephone dial pulses as inked dashes on paper tape. Dial impulse recorder. A touch tone decoder performs the same function for a touch tone telephone.

Physical Search - One of the phases of a TSCM survey. Physical search includes visual inspection and electrical examinations.

PIC Cable - Polyvinyl Insulated Conductor. A cable containing multiple pairs of telephone wires.

Pin Hole - An air passage to a concealed microphone made with needles or miniature twist drill. The microphone must be sealed air tight at the inner end of the passage in order to pick up sounds properly from the other end. A small opening in a wall or ceiling into which a specially designed camera lens (pin hole lens) is inserted for viewing a designated area.

Plant - A confusing term sometimes meant to mean the act of installing an OCI, an actual OCI device, or a listening post.

Presence - A sense of "being there" felt while listening to stereo recordings.

Primary - The circuit that contains the transmitter and hookswitch. This circuit is connected directly to the central office during a conversation and in order to perform its job must allow direct current to flow through it. In most telephones, this circuit will contain only the transmitter, primary of the induction coil, the hookswitch, and the pulsing springs or contacts of the dial. Because it is necessary for the direct current to flow through the transmitter, there can be no capacitor in this circuit.

Protector - In telephone systems, a device designed to conduct to ground any high voltages which, by any means, comes to be present on a phone line.

Q

Quarter Wave Antenna - An antenna with active elements spanning a distance equal to one quarter the wavelength of the operating frequency.

Quick Plant - An audio bugging transmitter easily installed or dropped in target area.

R

Radio Frequency (RF) - Electro -magnetic waves used in radio communications to carry intelligence.

Rarefraction - Dispersion of air particles.

Receiver - A radio signal reception and demodulation device.

Reflector - In antennas, a parasitic antenna located away from the direction of the major lobe of the reception/radiation. Normally only one in number and usually behind the associated dipole. May alternatively consist of a mesh screen or an assembly or two or three elements equidistant from the dipole. By contrast : see "Directors".

RF Amplifier - Any amplifier designed to work at radio frequencies.

RF Detector - In countermeasures, an instrument used to detect the presence of a radio signal. Normally an untuned, very simple form of receiver.

RF Noise - Unwanted RF energy which interfers with clear radio reception.

RF Search - In countermeasures, the initial phase of a TSCM survey. A thorough examination of all radio frequencies within the range of available equipment.

Ring - In telephone systems, the wire in a pair which is connected to the negative side of the battery, the ring terminal of a switchboard phone plug, the right side terminal in a pair of terminals, (if vertically separated), and the ridge side of a drop wire, usually the red lead in an instrument mounting cord. Thus, the expression, red, right, ridge, bottom used as a memory aid in keeping correct polarity in telephone connections.

Ringer - To signal the called telephone. This is usually A bell made to operate on AC only and is isolated from the direct current of the line by means of a capacitor.

Ringer Circuit - Telephone bell and the electrical circuit that makes it work.

ROH - Receiver Off Hook, a standard drawing is on hook.

S

Scrambling - In voice security systems, a non -cryptographic effort to provide security against eavesdropping. By contrast : see "Ciphony".

Second Detection - In countermeasures, the demodulation of audio intelligence from a subcarrier. In radio, the demodulation is often called the second detector, the first detector being the hetrodyne mixer in a superhet receiver.

Secondary - The main circuit for the operation of the telephone receiver. This circuit receives its power from the primary through induction and is usually arranged so that direct current does not flow through the receiver. It quite frequently does contain a capacitor, but it always contains the receiver and the secondary winding of the induction coil.

Series Parasitic Transmitter - In telephone systems, a low power transmitter installed in either conductor of a line pair. It serves as a WCI device and takes its power from the line when the phone is in use. It does not operate when the instrument is on -hook.

Series Radio Tap - Radio transmitter which usually obtains power from the telephone line to which it is attached and is installed in series or in line with one line.

Shotgun Microphone - A microphone in a chamber connected to several tubes of different lengths which are bundled together. Sounds arriving from the off end of the tubing bundle travel the same distance through the tubes to arrive in -phase while sounds from the side have a different distance to travel down each tube and tend to arrive out of phase with one another. The device must be exposed entirely in the same air mass with the target as the sounds in order to have the desired directional effect.

Side Band - The small band of frequencies produced adjacent to a main radio carrier frequency which contains the basic audio information.

Sidetone - The sound heard in the receiver that was picked up by the transmitter of the same telephone.

Signal to Noise Ratio - In RF and audio signals at any point in the surveillance system, the relative power ratio between desired signal and noise.

Snuggling - The tuning of a surveillance transmitter into the upper or lower edge of a wideband signal such as a commercial FM broadcast or a TV station. This technique is intended to hide a low power device from detection by conventional receivers.

Soft Room - A room furnished with carpets, drapes, and overstuffed furniture in which the echo is reduced considerably. Such rooms pose fewer problems to surveillance installations. By Contrast : see "Hard room".

Spare Pair - In telephone systems, a pair of unused wires in a cable.

Spider - A power extension cord with several duplex outlets fed through a single grounded line. It serves to insure balanced voltage and ground connections for equipment in a listening post.

Spike Microphone - A colloquial term used to describe a contact microphone to which a long rod is attached through a double sided wall. It has limited applications in technical surveillance.

Standing Waves - A pattern of radio energy in space which varies in intensity from point to point caused by reflections of radio signals.

Sub -carrier - An RF technique which requires two demodulations to get back audio.

Sub -harmonic - A lower fractional multiple of a fundamental frequency.

Sub -set - Short for subscriber's set or telephone.

Substation - Short for subscriber's station. Includes all equipment installed at the user's premises.

Station - Usually applied to one telephone of a key telephone system.

T

Tertiary - Or third circuit used in the voice part of a telephone. In some telephones, this will include a third winding of the induction coil, on other sets the same function will be performed using the voltage drops and counter EMF developed across various resistors and capacitors. This circuit is also known as the anti -sidetone circuit in that it reduces the amount of sound heard in the receiver that has been picked up by the transmitter of the same telephone. The circuit is used in practically all modern telephones, but every manufacturer seems to think he knows the best way to do the job, resulting in wide differences in this circuit.

Third Wire Bypass - In telephone systems, a method in which the yellow wire in the instrument mounting cord is used to gain access to either the carbon microphone or dynamic earpiece (and to bypass the hook -switch).

Time on Target - The period of time spent in a target room or area making a technical surveillance installation.

Tip - In telephone systems, the wire in a pair which is connected to the positive side of the battery. The tip terminal of a switchboard phone plug, the left hand terminal in a pair of terminals (if side by side), the top terminal of a pair of terminals (if vertically connected), and the wire opposite to the ridge of a drop wire. The expression "Tip -Top" is used as a memory aid for the vertically separated terminals. Usually, the green lead in an instrument mounting cord.

Tone Masking - The use of audible toneage to disguise the content of an ongoing conversation as a form of scrambling. Theoretically, the masking tones can be later filtered or cancelled out to restore intelligibility to the original voice signal.

Transducer - A device which converts energy from one form to another. Microphones and antennas are transducers.

Transmitter - The microphone of the telephone instrument. Also, a device that produces and radiates RF energy via an antenna.

Trunk - The main cable originating at the central office.

U-Z

Voice Muffler - A communications security device using microphones attached to plastic cups so that two or more people can converse by whispering directly into a cup with the microphone cable leading directly into a miniature amplifier to drive headphones. The device is sometimes used to hold secret conversations in a room known or suspected of being equipped with a listening device.

Voice Operated Switch (VOX) - An electronic circuit used to actuate a transmitter, recorder, or other device when sounds in the area reach a preset level.

Vulnerability Area - The area between a subscriber and the central office where the line pair is susceptible to WCI operations.

Wet Finger Method - In telephone intercept work, a method of using a finger moistened as a variable resistor to slowly charge a lineman's test set so as not to cause an audible click during attachment to line pair.

Wire Communication - According to Public Law 90 -351, any communication made in whole or in part through the use of facilities for the transmission by the aid of wire, cable, or any like connection between two points.

Wiretap - A wire communications intercept.

Wireless Microphone - A miniature radio transmitter which broadcasts the voices of someone wearing it for use on sound stages to free performers from the encumbrance of hand held microphone wires. Wireless mics are not well suited for use as surveillance transmitters due to their being wideband FM and often being fitted with close talking microphones which inhibit pickup of voices over two feet away. Additionally, many wireless microphones operate in or immediately adjacent to commercial FM bands and are therefore subject to accidental detection.

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