3.1
In general, definitions set by the International Telecommunications Union and published in the ITU-T (formerly CCITT) Recommendations apply throughout this Specification. Nevertheless, some ITU-T definitions are not particularly informative for those unfamiliar with telecommunications engineering. In the circumstances, the following definitions are supplemented by explanatory paragraphs which elaborate on the formal wording.
3.2
Additional definitions are provided in Specifications PTC 100, PTC 101 and TNA 102. Nevertheless, some definitions are repeated in this Specification in order to explain aspects which directly relate to its requirements.
Acoustic stability: is the ability of a telephone device to prevent oscillations occuring when sound waves from the earpiece are fed back into the mouthpiece.
* Such feedback can occur when a telephone handset is placed face down on a hard flat surface.
Answering machine: is any form of automatic device, whether stand alone or integrated into some other class of equipment, which provides facilities to answer a call without human intervention.
* Answering machines and telephone instruments are now often combined into a single integrated item of equipment. In such cases, the complete unit will be regarded as an answering machine.
Artificial ear: is a measuring device, the input of which has an acoustic impedance equivalent to the acoustic impedance of the average human ear, and forms part of part of an "artificial head".
* It comprises an acoustic network and a measurement microphone which permit calibration of earphones used in audiometry and telephony, and is used in the measurement of loudness rating.
* Reference ITU-T, Recommendations P. 57:1993 and P. 65:1993.
Artificial head: is a purpose-designed jig which includes the artificial ear and mouth and ensures that they are in the correct relationship for measurement of the loudness rating of telephones.
* The head also provides facilities to clamp a telephone handset in the designated speaking position.
* The equipment includes computer-controlled frequency generators and amplifiers, audio spectrum analyser, and other specialised electronic test equipment, all set up to provide rapid and accurate measurements of the various performance parameters.
Artificial mouth: an electro-acoustic transducer used for the testing of microphones at close speaking distances, and forms part of an "artificial head".
* Reference ITU-T, Recommendations P. 51:1993 and P. 65:1993.
Auto-answering: is the procedure by which equipment automatically answers an incoming call on detection of the ringing voltage.
Auto-answering mode: is the mode in which the equipment is ready to automatically answer an incoming call.
* Equipment can often be set to answer automatically or be set for manual answering while the user is present. Requirements for automatic answering apply only while the equipment is in the auto-answering mode.
Auto-calling: is the function whereby equipment automatically initiates a call without deliberate human intervention.
* "Auto-calling" does not include calls made by devices using functions such as memory dialling or "last number redial" which are initiated by manual operation of a key or similar action. Such functions are categorised as 'Auto-dialling'.
Auto-dialling: is a function whereby equipment automatically dials a number following some form of manually initiation.
Bridging equipment: is high impedance equipment designed for connection in parallel with customer terminating equipment, but which does not provide any form of line termination.
* Bridging equipment remains connected to the line whether the terminal equipment is on-hook or off-hook. It does not provide any line control function, but is used for such functions as monitoring, detecting, etc.
Call waiting: is a network service provided by Telecom whereby a brief tone is applied repeatedly on a call already in progress to indicate that there is another incoming call waiting for the customer concerned.
Caller Display: is the Telecom service which, using the on-hook data transmission facility, provides for the display of the calling telephone number on the called party's terminal equipment.
* Otherwise known as "calling line identification".
* "On-hook data transmission" and "Analogue Calling Line Identification Presentation (Analogue CLIP)" are described in Technical Document TNA 102.
CNG Tone (calling tone): Is an interrupted tone (1100 Hz) transmitted by automatic calling non-voice equipment.
* Reference ITU-T Recommendation T. 30:1993.
dBmP: is the absolute psophometric power level with respect to 1 mW, expressed in decibels. (See also separate definition of 'psophometric'.)
* Psophometric weighting for use on telephone-type circuits is as indicated in CCITT Blue Book, Recommendation O. 41.
dBm0P: is the absolute psophometric power level expressed in decibels with reference to a point of zero relative level (i.e. 0 dBr point).
dBPa: is the absolute sound pressure level with respect to 1 Pa, expressed in decibels.
dBr: is the relative power level at a given point on a circuit with reference to a point of zero relative level (i.e. 0 dBr point).
* Digital codecs used in the Telecom network are defined as 0 dBr points, ref. ITU-T Recommendation P. 66:1993, Clause 3.
dBV: is the absolute voltage level with respect to 1 V, expressed in decibels.
Decadic: is the form of call initiation signalling which makes use of one or more timed disconnections of the line current.
* Otherwise referred to as "loop-disconnect" signalling or "pulse" signalling. It is the form of signals sent by an ordinary rotary telephone dial.
Distinctive Alerts (DA): are the four different ringing cadences (DA1 to DA4) used on PSTN lines, and which may be used as a means of identifying particular items of CPE.
* Typically used as a means of indicating a specific person or function required by the caller (e.g., facsimile, modem, telephone, etc), or the nature of the call (on Centrex). Separate numbers are allocated to individual cadences when this service is provided (see Technical Document TNA 102).
* This service may also be known as "Private Ringing".
Distinctive Alert decoders: is a customer device which decodes the incoming DA code and applies ringing to the required item of CPE.
* There are two types of Distinctive Alert decoder, known as Types 1 and 2, which are described in the text of Section 11.
DTMF (Dual Tone Multi-Frequency or touch tone): is the signalling method used both for call initiation and for the accessing of other services following connection of a call.
* Two tones are sent simultaneously to line for each digit, hence the word "dual". The system provides high immunity from spurious signals such as speech and noise not intended to be recognised as signalling information.
* The system used in New Zealand is to the current world standard described in the CCITT Blue Book, Recommendation Q. 23.
Echo return loss: is a weighted integral of the return loss/frequency function over the band 300 - 3400 Hz.
* See also definition of 'return loss'.
* To calculate 'echo return loss' from the individual return loss measurements at given frequencies, the approximation formula for derivation of 'echo loss' given in ITU-T Rec. G. 122:1993, Annex B.4 is used.
Facsimile: is a system for transmitting and receiving text and images. For the purposes of this Specification the medium over which the image information is carried is the Telecom Public Switched Telephone Network.
Full current: is the current drawn by any item of terminal equipment when connected directly to a 50 V, 400 ½ source in the off-hook condition.
* "Full current" is used for test purposes and defines the maximum current that can be drawn under zero length line conditions.
* On some exchanges operated by Telecom, the line current 'limits' at 80 mA maximum.
Handover: is the process of transferring a call, which is in progress, from one item of terminal equipment to another while maintaining the connection.
Handset: is a rigid combination of telephone microphone and telephone receiver in a form convenient for holding simultaneously to mouth and ear respectively.
* The geometric relationships between the receiver and microphone positions for optimum transmission performance are given in CCITT Blue Book, Recommendation P. 35.
Handsfree facility: is the provision of a loudspeaker and amplifier within the telephone such that calls may be established without lifting the handset.
* Call progress can be monitored and the handset only needs to be picked up for actual conversation when the called party answers. This facility should not be confused with the separately defined "Loudspeaking facility".
* With the handsfree facility, the only microphone provided is that within the handset and the loudspeaker is disabled whenever the handset is "off-hook".
Headset: is an assembly comprising transmit and receive transducers, but without signalling, ringing, or full transmission circuitry, designed for fitting on the user's head in order to leave the hands free for other activities.
Hold: is any temporary condition applied to a line while a call is in progress to maintain that call and permit its subsequent retrieval.
Hookswitch: is the general term covering any switch or other device which is operated when the handset is returned to its normal rest position.
* "Hookswitch" includes any control buttons used to initiate or terminate a call and also includes any switch feature of "one-piece" or novelty telephones which performs the ON/OFF function.
* See also definitions for "On-Hook" and "Off-Hook".
Hookswitch flash: is the momentary operation by the user of the Hookswitch to perform a "re-call" or similar function.
* This causes a brief interruption to the line current, but the duration is not long enough to be detected and interpreted as the completion of the call.
Informed user: is a person who is familiar with the use of certain non-standard specialised equipment in order to initiate or receive calls.
* This term includes users who are situated remote from the specialised terminal equipment concerned.
* Such equipment will often be automatic calling or answering devices.
* See also "Naive user".
Insertion loss: is the ratio of the loss or gain through a network when a device is connected to that when the same device is not connected, normally expressed in dB.
Inter-digital pause: is the interval between successive DTMF tone bursts (or decadic pulse trains) in a series of digits.
Key Telephone System (KTS): See definition of "PABX Type 2".
Last number re-dial (LNR or LND): is the process of sending DTMF (or decadic) signals, manually dialled and stored in the sending device during the previous call attempt, to establish a connection.
Line grabbing: is the facility whereby an item of equipment, whether under manual or automatic control, may disconnect any other terminal equipment from its line and seize that same line to either terminate or initiate a call.
Loop current: is the standing d.c. current drawn by any equipment in the off-hook condition.
* The loop current is dependent upon the resistance of the equipment, the line length and any current limiting by the feed voltage.
Loudness Rating (LR): is a measure, expressed in decibels, for characterising the loudness performance of complete telephone connections, or parts thereof, such as the sending system, line, or receiving system.
* Reference ITU-T Recommendations P. 64:1993 and P. 65:1993, and also CCITT Blue Book, Recommendation P. 76.
* Loudness rating is an internationally accepted method of objectively measuring the performance of telephones from the mouthpiece to a given point on the line, and vice versa to the earpiece. The approach enables computer-controlled measuring equipment to be used for making quick, accurate and, above all, repeatable tests.
* A loudness value is the result of a calculation based on fourteen separate measurements made at pre-determined frequencies within the normal telephony frequency range, each measurement being "weighted" according to its effect as perceived by the human ear when listening to normal spoken words.
* The loudness measurement value is actually the loss involved in the circuit under test, relative to an internationally accepted reference standard. Thus the higher the loudness value the quieter the perceived signal volume. A negative value occurs when the loss is actually less than that of the reference standard.
* Loudness is closely related with Sidetone in any assessment of telephone performance - see definition of "Sidetone".
* See also definitions for "Artificial ear" and "Artificial mouth".
Loudspeaking facility: is a facility to permit several people to take part in a telephone conversation by incorporating a microphone usually, but not necessarily, separate from the one in the handset, which is designed to pick up speech in the near vicinity of the telephone set.
* It incorporates an amplifier and a loudspeaker for the reception of incoming speech.
Message acceptance tone (beep): is a brief tone or 'beep' signal to a caller that an automatic answering device is in the receive mode and is ready to accept and record a message.
Message waiting: is indicated by a 'blip' in dial tone to indicate to the customer that there is a message waiting on the "Call Minder" sevice.
Modem: is the signal conversion equipment which converts the digital signal output from a terminal (or computer) into analogue signals suitable for transmission over a Telecom line, and vice versa, by a process of modulation and demodulation.
* 'Modem' is a contraction of modulator- demodulator.
Monitoring: is the detection of signals on a line (both supervisory and /or voice) without taking an active part in a communication over that line.
* Monitoring equipment may be designed to detect specific line conditions such as whether the line has been seized or not, the presence of ringing, or it may monitor the actual communication itself.
* Equipment monitoring a line will usually, but not necessarily, be in the on-hook high impedance mode.
* The use of such equipment is subject to the Privacy Act 1993, the Telecommunications Act 1987 and the Crimes Act 1961.
Monitoring facility: (in the context of recording equipment) is the provision of a device which monitors all signals present on a line while a call is in progress.
Monitoring facility: (in the context of automatic calling equipment) is the provision of a loudspeaker and amplifier for incoming signals such that call progress can be monitored.
Mute: the temporary suppression of any speech transmission facility provided by an item of terminal equipment.
* Mute is used for security or confidentiality purposes, and to enhance received speech perception in noisy ambient conditions.
Naive user: is a person with no special knowledge of the characteristics of a particular complex system and having no specialised equipment that may be necessary to deal with a call from such systems.
* This concept is particularly applicable to equipment which has automatic calling or answering facilities.
* The concept of a "naive caller" is dealt with in British Standard BS 6789 and the definition has been amended for New Zealand applications to cover anyone who is not privy to the special requirements of an automatic system. A system can thus have special characteristics in order to provide some degree of security against unauthorised users or those who are accidentally connected to the system.
* Application of the naive user concept provides for particular Telepermit grant conditions to be negotiated in some special circumstances, especially where professional equipment is involved or where there is some need for additional security.
Noise: is any unwanted electrical energy which can be measured psophometrically at the output of a device or line.
* See also definition of "Psophometric".
* For the purposes of this Specification, 'noise' also includes unwanted electrical energy at frequencies outside the normal speech band of 300 Hz to 3400 Hz.
Non-terminating device: is a series connected device which is not capable of originating or answering a call when connected to the PSTN, and is associated with a separate terminating device.
* See also definition of "series connected device".
Off-hook: is the condition where the equipment is connected to line and is used to initiate or take part in a call (sometimes referred to as "on-line").
On-hook: is the condition where the equipment is connected to line in the idle state awaiting receipt of an incoming call or available to initiate a call (sometimes referred to as "off-line").
* The above terms are derived from the term "hookswitch", which is used to describe any device which changes the status of the equipment from "on-hook" to "off-hook" or vice versa.
PABX: is a form of telecommunications system designed for use in a customer's premises which provides full switching facilities between individual extension devices and the Telecom PSTN.
* For the purposes of defining interface requirements a PABX system may be considered to provide a similar range of conditions to that of a public exchange line.
* For the purposes of this and other PTC Specifications, and TNA documents, the term "PABX" embraces all Private Automatic Branch Exchange (PABX), Key Telephone System (KTS), Small Business Exchange (SBX) and other equipment intended for installation in a customer's premises to switch calls between separate telephone lines.
* For Telepermit purposes, it is necessary to divide PABX's/KTS's into two defined categories.
PABX Type 1: is a 4-wire switching device (digital or analogue) which, by its very nature, is designed to have an inherent 2 - 3 dB transmission loss between extension and 2-wire analogue trunk ports.
* Reference Specifications PTC 107, PTC 108 & PTC 109 for full details. Larger PABX's are normally Type 1 and may also have provision for digital trunks.
PABX Type 2: is a 2-wire analogue switching device without networking facilities or the capability for such facilities, which has a nominal 0 dB (¾1 dB) transmission loss between extension and analogue trunk ports.
* KTS's can normally be categorised as Type 2.
* For Telepermit purposes, Type 2 can normally be tested against this Specification.
Professional equipment: is equipment of a special nature, not generally intended to be offered for sale to the general public.
* Professional equipment is required to be granted a Telepermit before it is connected to the Telecom network. However, because of its special nature, and the fact that the purchaser will usually have some formal performance agreement with the supplier, there may be variations in the conditions which are applied to the grant of a Telepermit.
Proprietary interface: is a company or industry interface that does not conform to national or international standards.
* A proprietary interface may conform to an industry standard not used by Telecom, but proprietary to a particular manufacturer. Such an interface may be acceptable for Telepermit purposes if it is not used for direct connection to an interface specified Telecom.
Psophometric: is the term used to describe a method of measuring noise within the speech band while weighting the value of each frequency component present in accordance with its relative effect on the human ear.
* Such measurements are made with a psophometer; which is a voltmeter fitted with a standardised frequency weighting network and calibrated to indicate noise power in psophometric units (dBmP).
* The weighting coefficients defined in CCITT Blue Book, Recommendation O. 41 for telephone circuits and weighted to a reference tone of 800 Hz are used by Telecom for telephony purposes.
PSTN: is the Public Switched Telephone Network
* New Zealand's PSTN services may be provided by a number of different Network Operators; see also "Telecom PSTN".
Quantity: is any batch, order or shipment from which a sample is drawn.
* The word "Quantity" is used to avoid any confusion with the formal meaning of the word "batch" to quality assurance personnel.
Recall: is the procedure used to re-connect the register function of a switching system to enable additional features of that system to be used while a call is in progress.
Repeat calling: is the function whereby equipment will automatically make a second or subsequent attempt to call a wanted number without intervention by a user.
* Repeat calling does not include functions such as "Last Number re-dial (LNR)", which have to be initially keyed by the user before they are activated. However, any function which is automatically activated is included.
Return loss: is a quantity associated with the degree of match between two impedances in a 2-wire speech path, expressed in decibels and given by the expression:-
Return loss of Z1 versus Z2 = 20 log10 I(Z1 + Z2)/(Z1 - Z2)I dB
* Reference ITU-T Recommendation G. 122:1993, Annex B1.
Ring trip: is the process whereby the exchange ringing signal is automatically stopped when a suitable direct current path is connected across the line.
* The capacitor in the on-hook termination blocks the path for any direct current, but allows alternating current to flow through the ringers. A d.c. path is provided when the call is answered and the current then flowing is referred to as the loop current.
Ringer (or ringing detector): is any device which responds to the alternating voltage applied to a telephone to indicate an incoming call.
* It should be noted that operation of a "ringing detector" does not indicate that an incoming call has been answered. It simply indicates the presence of an incoming call.
Ringer Approximate Loading (RAL): is an arbitrary rating for a telephone ringer which represents, in numeric terms, the approximate current that it draws from a ringing signal.
* The reference value for RAL is based on the on-hook admittance (reciprocal of the impedance) of a reference telephone. This has now been replaced by 'Ringing Number (RN)'.
Ringer loading: is a rating for a ringing device, based on the ringing current drawn when that device is connected in parallel with other ringing devices on the same line.
Ringing Number (RN): is an arbitrary rating for a ringing device which represents, in numeric terms, a combination of its sensitivity and loading on the ringing supply.
* The RN of a device is the greater of the numbers allocated for 'ringer sensitivity' and 'ringer loading'.
* RN supersedes RAL. It is intended to provide a Telecom customer with an effective means of assessing the maximum number of ringers that may be connected to the same line and still ensure a reliable ringing performance.
Ringer sensitivity: is a rating number allocated to a ringing device indicating the sensitivity of its response to ringing current on a line.
Sample: is a number of items, randomly selected from a larger quantity, for the purposes of statistical prediction of the characteristics of the whole quantity of items.
Scrambler: see "Voice privacy equipment".
Series connected device: is any customer premises equipment designed for connection between a PSTN line and another item of customer equipment.
* The functions of a series connected device are auxiliary to those of the terminal device to which it is connected. Typical examples are distinctive alert decoders, fax switches, automatic diallers, caller display adjunct units, call monitoring equipment, etc. This term does not embrace items such as jackpoints, wiring, etc.
* A series connected device may have either a terminating or non-terminating function, and may also include bridging equipment in some cases.
* Certain types of CPE incorporate a 2-wire/4-wire/2-wire process. Examples of this are some small key systems and also equipment which facilitates the extension of a PSTN line (foreign exchange) or PABX extension to a distant location. These examples provide for amplification on the 4-wire path of the equipment, but are connected 2-wire at both end interfaces and effectively fall within the above definition of 'series connected' equipment.
Sidetone: is the reproduction in a telephone receiver of sounds picked up by the microphone of the same telephone.
* For telephone evaluation purposes, sidetone is measured as the "Sidetone Masking Rating" (or "STMR"), which is part of the Loudness Rating concept. STMR is a measurement related to an ITU-T standard test system and it also takes into account the overall effect of what the speaker would hear of his own voice in normal conversation.
* Reference ITU-T Recommendations P.64:1993 and P. 65:1993.
Simple telephone: is an apparatus for voice communication over the PSTN, for which both initiation and termination of the call is under manual control and involves the mechanical lifting of a part or the whole of the apparatus, and incorporating a key pad (or rotary dial) to provide signalling.
* The term "simple telephone" relates to its basic operation, not to its facilities or features. Thus, a multi-button telephone with repertory dialling, clock calculator, etc., may be included within this definition.
* A simple telephone may be directly powered from a line, powered by internal batteries, or via power units connected to the public supply.
* For the purposes of this Specification, a simple telephone does not include any instrument capable of directly accessing two or more telephone lines.
Supervisory equipment: is any equipment intended to monitor and/or detect some parameter and which is capable of initiating or terminating a call in order to pass the information over the Telecom line to some remote point.
Supervisory system: is the combination of some central control equipment, the Telecom network, and one or more items of supervisory equipment which, together, form a complete telemetry system.
* Such equipment has generally been regarded as "professional" equipment in the past, but the growth of security, burglar and fire alarm systems for normal residential applications has led to such equipment being classified as a standard retail product.
System-dependent terminal (or device): is an item of customer premises equipment specifically designed for use with, and dependent on, a particular type or make of customer switching system (or other customer equipment).
* System dependent devices are not considered suitable for direct connection to a standard Telecom PSTN without the 'mother' system. They usually incorporate a proprietary interface.
* Customer switching systems normally take the form of PABX's or key telephone systems.
Telecom PSTN: is the Public Switched Telephone Network provided and operated by Telecom New Zealand Ltd.
* The PSTN also includes the connection to other switching systems (e.g. PABX's) which may be installed in private premises, but which are directly connected to the PSTN. It does not include the interconnection of private switching systems via leased lines.
* Telephones suitable for the Telecom PSTN are also often suitable for use with PABX and Key Telephone Systems. Some systems however require special purpose-designed telephone instruments, described as 'system dependent' instruments, to provide their particular features.
Telephony device: is any device having the ability to convert acoustic signals into electrical signals, or vice versa, for the purposes of transmission over a telephone network.
* Such facilities are normally known as 'electro-acoustic' facilities.
Terminal equipment port: is any port on a series connected device to which a terminating device can be connected.
Terminating device: is any device designed to terminate a PSTN line for the purpose of either initiating or answering calls over the network.
* See also "Series connected device", which can also be a terminating device.
* Certain products are capable of functioning as a "terminating device" or a "non-terminating device" depending on the circumstances. An example is a fax switch which answers a call, and then extends the call to another terminating device.
Three-wire connection: refers to the plug and jack wiring arrangement used for connection of devices to the Telecom network using three wires, the third 'shunt' wire being used for ringer connection.
* This arrangement using a 'BT' socket and plug to BS 6312:1985 was the standard method used between 1983 and 1996 for connection to the Telecom PSTN. It involves the 3-wire connection of premises wiring between a master jack and a series of secondary jacks such that all devices connected are in a 3-wire parallel arrangement.
Through return loss: is the degree of match between a reference impedance and the impedance of the line port of a series connected device, when the terminal device port of the same device is terminated with an equivalent reference impedance.
* See also definitions of "series connected device" and " return loss".
* The reference impedance referred to is normally "BT3".
Timed break recall: is a manually initiated break of a pre-set duration in the holding loop of a telephone when in the "off-hook" condition, for extending a recall signal to the exchange. Two-wire connection: refers to the arrangement which provides for connection of 2-wire devices such that the ringing current is taken directly from the 2-wire line.
* 2-wire devices can also be connected to 3-wire customer premises wiring.
Voice privacy equipment: is equipment designed to provide for the security of voice communications by means of two or more matched devices which encode voice signals sent to line, and reconstitute received coded signals into intelligible voice signals.
* Privacy equipment is sometimes known as "voice scramblers".
Volume unit (VU): is a unit of measurement used for determining the level of speech signals transmitted over a transmission line.
* On CPE, VU's are used as a means of assessing the performance of voice recordings on answering machines, voice mail equipment, etc.
* For Telepermit purposes, VU's are measured using a volume unit meter as specified in CCITT White Book, Volume V, Supplement No. 11.
* There are a number of variations around the world of the types of VU meter, and also in the definition of VU's. Comparisons between different types of volume meters are given in ITU-T Rec. P. 52:1993.