telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

, a transmission level point (TLP) is a physical test point in an

electronic circuit An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical ...

, typically a transmission channel, where a test

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

may be inserted or measured.Whitham R. Reeve (1992) ''Subscriber Loop Signaling and Transmission Handbook—Analog'', IEEE Press, p.229 Typically, various parameters, such as the

power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...

of the signal, noise, or test tones inserted are specified or measured at the TLP. The nominal transmission level at a TLP is a function of system design and is an expression of the design

gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...

attenuation In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable att ...

(loss). Voice-channel transmission levels at test points are measured in decibel-milliwatts (dBm) at a

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of ca. 1000

hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...

. The dBm is an absolute level with respect to 1 mW. The TLP is thus characterized by the relation: :TLP = dBm — dBm0 When the nominal signal power is 0

dBm DBM or dbm may refer to: Science and technology * dBm, a unit for power measurement * DBM (computing), family of key-value database engines including dbm, ndbm, gdbm, and Berkeley DB * Database Manager (DBM), a component of 1987's ''Extended Edi ...

at the TLP, the test point is called a ''zero transmission level point'', or ''zero-dBm TLP''. In general, the term ''TLP'' is commonly used as if it were a unit, preceded by the nominal level for the test point. For example, the expression ''0TLP'' refers to a '. At a −16TLP, the measured level of 0dBm is +16dBm0. The level at a TLP where an

end instrument In the context of telecommunications, a terminal is a device which ends a telecommunications link and is the point at which a signal enters or leaves a network. Examples of terminal equipment include telephones, fax machines, computer termina ...

, such as a

telephone A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into e ...

set, is connected is usually specified as 0dBm.

References

{{reflist Telecommunications engineering

See also

References