TSCM (technical surveillance counter-measures) is the original United States Federal government abbreviation, denoting the process of bug-sweeping or electronic counter surveillance. It involves all forms of intelligence and counter intelligence operations, communication and information security and electronic countermeasures.
The United States Department of Defense defines a TSCM survey as a service provided by qualified personnel to detect the presence of technical surveillance devices and hazards and to identify technical security, which could aid in the conduct of a technical penetration and compromise, of the surveyed facility. A TSCM survey will provide a professional evaluation of the facility’s technical security posture and normally will consist of a thorough visual, electronic and physical examination, of both within, and out of the surveyed facility.
A viable TSCM programme is equally concerned with denial as with detection since one cannot separate physical security from technical security. Most bugs transmit information, whether data, video, or voice, through the air by using radio waves. The standard counter-measure for bugs of this nature is to search for such an attack with a radio frequency (RF) receiver. Lab and even field-quality receivers are very expensive and a good, working knowledge of RF theory is needed to operate the equipment effectively.
Since it is easier to tap the domestic telephone of a person, most bugs installed, have been planted with relative ease within domestic environments. Thus, the majority of eavesdropping devices  which are habitually used in houses  are more often of the cheap varieties which could be manufactured by most any, electronic technician or bought for as little as 50.00 U.S dollars. The drawback of this approach is that you often get what you’ve paid for, so that many of the cheaper version of bugs do not work as effectively as the more sophisticated ones.
The choice of method of attack and, to a large degree, the device(s) chosen for employment will be dictated by the environment under attack. The Target Analysis will be as complete as possible and will influence the entire option sequence that follows. For example, if the Target Analysis shows  that a surreptitious entry, while necessary will be an extremely risky venture, then the device chosen must be highly dependable and require little or no servicing, since the prevailing circumstances do not allow  re-entry of the targeted area with relative ease, to change batteries or a tape.
Conventional methods of eavesdropping to gather intelligence requires the use of wiretaps for the interception of telephone conversations, also the use of hidden microphones, transmitters, etc. for the interception of room conversations. In other words, two different types of eavesdropping devices are necessary to gather the maximum amount of audio intelligence.
Thus you can be bugged in the following ways:
1. From within the telephone exchange or main distribution frame (MDF) the way governments more often do it.
2. From within the cabinet located on the street, which is relatively difficult to do.
3. By compromising the private branch exchange (PBX) that serves a particular business or office.
4. By attacking the connection which runs from the pole to the building.
5. Through the use of highly sophisticated remote gadgetry.
6. The placing of microphones in your office, home or car to pick up audio.
7. By tapping your phone line, or through a modification of the telephone instrument.
8. By placing a key logger or programme on one or more PCs that send everything you do on your computer out to another site on the internet.
The person listening to the bug can be connected in a few ways:
1. A hard-wired connection to the telephone wiring in the building, since a telephone line always has power, it could work forever.
2. An RF transmitter that broadcasts over the radio from your office, home or car. A modified cell phone through its RF capacity, can work almost anywhere, by being connected undetected to a car’s battery.
3. The exact GPS location of a vehicle and its occupants can be broadcast, so one’s exact location could be determined.
4. An internet connection through your always-on broad band connection, which could be digitizing telephone calls, room, audio and computer keystrokes and screen, sending information to another site on the internet.
When the bugging of the Police Commissioner’s telephone line was brought to my attention, given the quality of the audio recording and my knowledge of the commissioner’s office and its outlining areas I immediately felt that the audio was not obtained by way of a sophisticated remote device, but was most likely obtained, through what is known as a hook switch bypass. While all of the components of a standard telephone instrument interface with various other components throughout the network, it is the hook switch which controls (turns on and off) many of their functions.
Although the hook switch bypass is not recognised as a conventional form of wiretapping, this simple technique of modifying the telephone instrument allows the eavesdropper to intercept both telephone and room conversations without being concerned about hidden devices, running wires, or changing batteries inside the target’s room. The use of most of the other available methods, would have defeated the purpose, since attempts to transmit signals out of the  police headquarters, would not have survived the severe  interference and distortions caused by the many power transformers present in the immediate  vicinity.
A conversation I had with the Commissioner in question several months later confirmed my suspicions.