Signal to noise chapter pdf download

Natural sampling is also called "flat-top" sampling. Flat-top sampling requires a sample-and-hold circuit. The Manchester line code provides strong timing information. Aliasing occurs when the sampling rate is too high. The basic DS-1 signal consists of 12 voice channels. Foldover distortion occurs when the sampling rate is too low. In DS-1, each analog voice channel is sampled times per second.

Sampling is actually a form of modulation. In DS-1, the bit rate for each voice channel is 56 kbits per second. The output of a sampler is a PDM signal. A T-1 frame contains bits.

The most commonly used digital modulation scheme is PCM. T-1 uses AMI. In PCM, the number of levels is the same as the number of bits. A T-1 cable can be twisted-pair copper wires. Foldover distortion is caused by: a. A T-1 line runs at 1. In DS-1, bits are sometimes "stolen" from the voice channel to be used for The immediate result of sampling is: signaling.

PAM c. PCM d. PDM Which of these is not a pulse-modulation technique: with fewer bits. PDM b. PWM c. PPM d. PPS Quantizing noise quantization noise : a. The dynamic range of a system is the ratio of: 1. The first digital code was the: a. ASCII code c. Morse code b. Baudot code d. In digital transmission, signal degradation can be removed using: a. Companding is used to: b.

TDM stands for: c. Ten-Digital Manchester d. Time-Domain Multiplexing d. Ten Dual-Manchester In North America, companding uses: 4. Hartley's Law is: a. In Europe, companding uses: 5. The Shannon-Hartley theorem is: a. Codec stands for: 6. The Shannon Limit is given by: a.

Coder-Decoder c. Code-Compression a. Coded-Carrier d. A typical codec in a telephone system sends and receives: 7. The Nyquist Rate can be expressed as: a. Compared to PCM, delta modulation: 8. Natural Sampling does not use: a. In delta modulation, "granular noise" is produced when: 9. Which is true about aliasing and foldover distortion?

They are two types of sampling error. You can have one or the other, but not both. Aliasing is a technique to prevent foldover distortion. The number of framing bits in DS-1 is: d. They are the same thing. Which coding scheme requires DC continuity: A vocoder implements compression by: a. AMI c. Manchester d. Manchester coding: d. Framing bits in DS-1 are used to: 3. In analog channels, the signal-to-noise ratio of an analog signal gradually The number of bits per sample in DS-1 is: channel.

The number of samples per second in DS-1 is: 6. The bit rate for each channel in DS-1 is: 7. ANS: correct In DS-1, bits are transmitted over a T-1 cable at: a. A T-1 cable uses: ANS: error, noise a. Manchester coding c. NRZ coding b. ANS: Time The number of frames in a superframe is: a.

ANS: limited A typical T-1 line uses: a. ANS: Hartley's ANS: Shannon-Hartley Compared to standard PCM systems, the quality of the output of a vocoder is: a. ANS: half ANS: Quantizing ANS: 12 ANS: superframe ANS: 1, one ANS: higher The telephone switching hierarchy is being replaced by a "flat" network topology. A "twisted-pair" is twisted to minimize "crosstalk". T ANS: 5 seconds 9. Use the Shannon-Hartley theorem to find the bandwidth required to send 12, bits per second if the number of levels transmitted is 8.

In a local loop, the red wire is positive. F ANS: hertz In a local loop, the TIP wire is positive. What is the Shannon Limit of a channel that has a bandwidth of hertz and a signal-to-noise ratio of 15? Local loops can carry voice signals in only one direction at a time.

F ANS: 16 kbps Local loops carry DC current. What is the minimum required number of samples per second to digitize an analog signal with frequency components ranging from hertz to hertz? Local loops carry signaling information. Loading coils allow high-speed data loads to be carried on a local loop. What is the approximate dynamic range, in dB, of a linear PCM system that uses 12 bits per sample? Typically, when a phone is on hook, a voltage of 48 volts appears across it.

T ANS: 74 dB 6. What is the approximate data rate for a system using 8 bits per sample and When a telephone is off hook, the DC voltage across it can drop substantially running at samples per second?

T ANS: 64 kbps The DC resistance of a telephone is about ohms. If bits were "stolen" from every DS-1 frame, what would the useable data-rate be for each channel in the frame? Assuming maximum input and output voltages of 1 volt, what is the output DTMF uses sets of 3 tones. F Chapter 8: The Telephone System The technology to "dial" telephone numbers was invented in A telephone from could not work on today's public switched telephone The central office uses 24 volts AC at 20 hertz to cause a telephone to ring.

F network. The local-loop is full-duplex. The public switched telephone network is changing from an all analog to a mostly digital system. Telephones usually contain a hybrid coil or an equivalent circuit. A LATA is a local calling area. To allow for "sidetone", a hybrid coil should be slightly unbalanced.

A feature of the public switched telephone system is that calls cannot be The signal levels in analog telephone systems have increased substantially over "blocked".

F the past years. Telephones connect to the central office via trunk lines. The signal levels in modern analog telephone systems are still based on 19th- century technology. Most local loops still use copper wire.

To allow multiplexing, the bandwidth of voice-grade telephone signals is 2. PSTN stands for: deliberately restricted. Public Switched Telephone Network b. Private Switched Telephone Network The net gain of a telephone system must be greater than 0 dB for an acceptable c. Primary Service Telephone Network signal level. Primary Service Telephone Numbers Too much gain in a telephone system causes "singing". POTS stands for: a.

Private Office Telephone System Echo suppressors prevent oscillations on long-distance telephone circuits. Primary Office Telephone Service c. Primary Operational Test System Echo suppressors can be switched off by a subscriber's equipment. Plain Old Telephone Service C-message weighting increases the bandwidth of a local loop.

LATA stands for: a. Local Access and Transport Area c. Local Area Telephone Access The reference level for measuring noise in a telephone system is 10—12 Watts. Local Access Telephone Area d. Local Area Transport Access In a telephone system, signal strength is given relative to the zero transmission 5. A LATA is a: loss point.

Central offices are connected by: DS-1 can be used to carry digital data that did not originate as a voice signal. When using DS-1 to carry data, it is common to use each channel to carry 64 kbps.

Local loops terminate at: a. Digital carriers up to T3 can use copper wires. Call blocking: a. Every "in-channel" signal is also an "in-band" signal.

In telephony, POP stands for: a. Post Office Protocol c. Power-On Protocol Common-channel signaling is being replaced by the more modern MF signaling. Point Of Presence d. The cable used for local loops is mainly: Common-channel signaling reduces opportunities for stealing telephone service. FITL stands for: a. Framing Information for Toll Loops c. Framing In The Loop Fiber In the Toll Loop d. Fiber-In-The-Loop DTMF stands for: a. Digital Telephony Multiple Frequency The range of DC current that flows through a telephone is: b.

Dial Tone Master Frequency a. Dual-Tone Multifrequency b. Loading coils were used to: In DS-1, bits are "robbed" in order to: a. The separation of control functions from signal switching is known as: b. ESS ISDN stands for: a.

Integrated Services Digital Network The typical voltage across a telephone when on-hook is: b. Information Services Digital Network a. Integrated Services Data Network b. Information Systems Digital Network The typical voltage needed to "ring" a telephone is: Basic ISDN has not been widely adopted because: a. The bandwidth of voice-grade signals on a telephone system is restricted in d. ADSL stands for: b. All-Digital Subscriber Line c.

Allocated Digital Service Line b. Asymmetrical Digital Subscriber Line d. Access to Data Services Line VNL stands for: a. Signal loss is designed into a telephone system to: a. The reference noise level for telephony is: 1.

The number of voice channels in a basic FDM group is: 2. Basic FDM groups can be combined into: 3. In telephone system FDM, voice is put on a carrier using: central office.

SSB b. DSBSC c. PDM d. PABX stands for: 5. Power Amplification Before Transmission to an overload of lines being used. Public Automated Branch Exchange d. Public Access Branch Exchange 6. ANS: digital SLIC stands for: a. Single-Line Interface Circuit c. Subscriber Line Interface Card 7. Standard Line Interface Card d. ANS: tip ANS: green ANS: seized ANS: common-channel ANS: packet ANS: TE1 ANS: asymmetrical ANS: conditioned ANS: suppressor 1. For a certain telephone, the DC loop voltage is 48 V on hook and 8 V off hook.

If the loop current is 40 mA, what is the DC resistance of the local loop? ANS: C-message 2. If the loop current is 40 mA, what is the DC resistance of the telephone? Which two DTMF tones correspond to the digit "1"? Use the table in the text.

In synchronous transmission, control characters in the data require special ANS: Hz and Hz handling, but flag sequences in the data do not. Calculate the dB of VNL required for a channel with a 3 ms delay.

T ANS: 1 dB HDLC is a bit-oriented protocol. If a telephone voice signal has a level of 0 dBm, what is its level in dBrn? ANS: 90 dBrn When receiving digital data, it is possible to detect errors, but not to correct them.

If C-weighting produces a dB loss, what would the signal level be in dBrnc0? In digital data transmission, bad frames are usually retransmitted. CRC codes are particularly good at detecting burst errors.

Hamming codes allow errors to be corrected without requiring retransmission. T Chapter 9: Data Transmission All schemes to detect errors require adding extra bits to the data being transmitted. Huffman codes are as good as CRC codes at detecting errors, but are faster. Data can be sent either in serial format or in parallel format.

Run-length encoding is a data-compression technique. For practical reasons, virtually all data communications is done in serial format. A "cipher" is, essentially, a secret code.

The first binary code was invented in Both "private-key" and "public-key" encryption always require the addition of 4. A character code is the same as a data code. T extra bits to the data. The old Baudot code is no longer used.

An advantage of public-key encryption is that it is not "computation-intensive", meaning a computer doesn't have to do many numerical calculations to unencrypt 6.

How fast data can be transferred is independent of the character code used. F decrypt the data. Both synchronous and asynchronous transmission require bit timing. A "digital signature" does not require the use of encryption. There is no "framing" in asynchronous transmission. A "mark" is the same as a binary 1. In practical terms, parallel data transmission is sent: Digital modulation is sometimes called "keying". Due to the "bursty" nature of most channel noise, simple parity is more or less useless.

The five-level teletype code was invented by: a. Western Union An advantage of using a UART is that "buffer overflow" cannot happen. Emile Baudot Synchronous transmission is much more efficient than asynchronous 3. Data codes are also called: transmission. In synchronous transmission, the data stream is used to "lock" the receiver's clock onto the transmitter's clock. Digital data that is not being used to carry characters is called: a. FIGS data c. Bit-oriented protocols are being replaced by the newer character-oriented b.

Character codes include: To maintain synchronization in synchronous transmission: a. ASCII stands for: d. American Standard Character-set 2 b. American Standard Code for Information Interchange HDLC: c. American Standard Code 2 a. Alphanumeric Standard Code for Information Interchange b.

The use of flags in SDLC requires: a. FEC b. ARQ 8. LF stands for: The initials ARQ are used to designate: a. Line Feed c. Line Forward a. Link Feed d. Link Forward b. UART stands for: d. Universal Asynchronous Receiver-Transmitter b. Unidirectional Asynchronous Receiver-Transmitter ARQ is used to: c.

Unaltered Received Text a. Universal Automatic Receiver for Text b. In asynchronous transmission, the transmitter and receiver are: d. FEC stands for: c. Fixed Error Control c. Forward Error Correction d. Forward Error Control d.

False Error Condition In asynchronous transmission, the time between consecutive frames is: VRC is another name for: a. ARQ c. LRC d. CRC stands for: In synchronous transmission, the frames are: a. Control Receiver Code c. Cyclic Redundancy Check a. Correct Received Character d. Cycle Repeat Character b. Huffman codes: d. Synchronous transmission is used because: c.

Run-length encoding is used to: d. In synchronous transmission, the receiver "syncs-up" with the transmitter by using: Public-key encryption: a. SDLC stands for: Synchronous Data Link Control c. Synchronous Data Link Character transmission. Synchronous Data Line Control d. HDLC is: ANS: Burst 5. ANS: stop ANS: even 8. ANS: mark, binary 1 ANS: burst 9. ANS: transitions Token passing can be implemented as a ring or as a bus.

T ANS: computation A token is used to control access to the network. A token is generated by a node wishing to access the network.

How many different characters could be encoded using a six-bit code? On a bus network, all traffic shares a common channel. T ANS: 64 CSMA networks must deal with "contention". Token-passing networks must deal with "collisions" between two tokens. Steam, water, gas cycles Q.. Auxiliary systems M.. Main machine sets common to L. Where several mechanical systems identified differently in data characters F2 and F3 are connected to one mechanical service system, the following code letters are used for the service systems on breakdown level 1 in the data characters concerned as follows: V Lubricant supply system W Sealing fluid supply system X Fluid supply system for control and protection equipment.

Feed water system Sealing fluid supply system for LB. Steam system LW. If several process-related systems are situated in one structure we designate this structure according to the main, most important system. Where individual structures for which separate structure codes exist are combined to form one structure, that structure is given the code of the most important individual structure. Special structures, ducting structures are designated in main group F1 with coding letter U and in subgroup F3 with following coding letters: X special structures, Y bridge structures, Z ducting structures.

Shared equipment Combined electrical and control and instrumentation equipment Combined electrical and control and instrumentation equipment, with or without a power unit e. If necessary, further grouping can be performed by using FN. Transducer Racks, Supports, Frames This auxiliary equipment is identified on breakdown level 1 using the code for the equipment location structure code , with the exception of auxiliaries for main machine sets and heavy machinery system code.

On breakdown level 2, transducer racks, supports and frames are identified by means of GZ. Junction Boxes On breakdown level 1, junction boxes receive the code of the structure and floor on which they are installed. Exceptions are junction boxes for main machine sets and heavy machinery, and junction boxes in electrical and control and instrumentation cubicles and cabinets; these are identified on breakdown level 1 according to the associated main machine or heavy machine and cubicle or cabinet respectively.

This code unit can be combined with any breakdown level as necessary for identification. Any combination of alpha and numerical symbols appropriate to the requirements is acceptable for the identification of connections. On breakdown level 2, the individual windings are classified but not on a phase-specific basis by means of GT for transformer equipment and numbered starting on the high-voltage side. Measuring Transformers The types of measuring transformers as well as their quantities in the given system are identified in breakdown level 2 by letters GT and three digits.

If the letters available are insufficient, FN may be used. In such instances the first character of FN has a classifying purpose. The second character of FN numbers the cubicles. Control and Instrumentation Equipment I - 5. Measuring Circuits Measuring circuits comprise analog signal acquisition, conditioning, distribution and measured data recording and indicating processing elements.

They are generally identified after the system within the interfaces of which the sensor is installed. Equipment Unit-Specific Analog Signal Processing and Measuring Circuits Equipment unit-specific analog signal processing elements comprise control and instrumentation equipment which is only provided for one equipment unit such as control interface, protective logics, instruments in the feeder and command termination for final control elements.

These analog signal processing elements receive the code of the equipment unit concerned. A2 identifies control and instrumentation functions e. Function-Interfacing Analog Signal Processing Where control and instrumentation equipment serves more than one process system identified in F2 and F3, the letter Y for generic control and protection systems may be used in the appropriate data character on breakdown level 1.

Control and instrumentation equipment which serves more than one main group may be identified under main group C for control and instrumentation, e.

Feed water system Control and protection system for steam, LY. Steam system common to LA. Conventional heat generation Unit control system L.. Steam, water, gas cycles CJA common to H. Main machine sets Given the possibilities shown in the table, it is not practicable to meet all possible requirements for identification of discrete process-related function e. Thus for example, it may be necessary to use items which are identified differently on breakdown level 1 main system and associated parts of auxiliary and ancillary systems in order to fulfil a given process-related task functional group.

Identification of the functional groups involved in process-related tasks so as to relate them to the principal task concerned may be performed by using the alpha characters in F F3 of the principal process-related task. In this application, however, a suitable identifier such as a prefixed Y should be used to indicate that a software coding unit is concerned, thus to rule out confusion with process-related codes.

This code is subject to agreement between the parties to the project. Gated analog signals representing physically similar direct measured variables are identified by means of a set number, e. Where signals or measured data are used to limit or suppress the original measured data, the processed output signals retain the code of the original measured data. Where measured data are corrected e. Identification in data character A2 is governed by the physical variable.

Closed-Loop Control Circuits The principles for the identification of measuring circuits apply analogously to the identification of closed-loop control circuits on breakdown level 1. Every control loop and every closed-loop control circuit comprises measuring, control and positioning elements regardless of whether electrical, pneumatic, hydraulic or other items of equipment are used.

Closed-loop controls are identified according to the controlles variable and not after the measuring circuits which serves the control or the final control element on which the control acts. Signals and Signal Applications Breakdown level 3 is used to identify signals and their applications. For this purpose, data character B1 can contain: X Signal origins Y Signal applications Z Gated signals No generally valid rules have been made for signal and application areas.

They should be established individually for different control and instrumentation concepts. Introduction Breakdown level 1 System function Serial no. The alphabetical symbols of this breakdown level are used to classify and divide the overall plant into subsystems, systems or building structures. It is not allowed to use any other letters.

Wherever possible, all three alphabetical symbols are permanently allocated, including their associated boundary constraints and task allotment in modern power plant technology. Coding letters of the main groups F1 are specified on next and the subdivisions in F2 and F3 are given in the present chapter II.

The numerical digits count and subdivide the unit e. The flag points in the direction of fluid flow. System One should remember, that the code of a system must consist of five symbols: three letters and two numerical symbols. Order according to voltage levels, counted from higher voltages to lower.

QCG Central chemical supply free for use e. QCU Central chemical supply free for use e. Introduction The table below shows the designation and type of data characters used for equipment unit code. Equipment Unit Identification In the process-related code which is the most important and mostly applied type of codes in every branch of engineering, the entire system is subdivided according to the function or process.

In this type of code, the breakdown level 2 contains equipment unit code. Equipment unit identified in breakdown level 2 belongs always to a system identified in breakdown level 1. Equipment unit code consists of 2 letters data characters A1 and A2 , 3 digits data characters AN and sometimes 1 letter data character A3 which can be, and often is omitted.

Equipment unit classification Serial no. Redundant zeros must be written, e. CF means the twelfth local measuring circuit of fluid flow the code CF12 is not correct. Details of equipment unit numbering are subject to agreement between the parties to the project.

It is a common practice to apply a grouping numbering of equipment units: the first numeral points the kind type of equipment unit identified in A1 and A2 e. Additional numbering code Serial no. Reactor, desorber. Filters in ventilation and air conditioning systems. Modern methods of digital systems programming and ability of efficient use of technical documentation require to use the concept of functional group positions A1 and A2 and number of the group positions An - three numerals depending on degree of complexity of automatic analog control system.

All signals in such automatic regulation system in breakdown level KKS 0, 1, 2, are described identically. This rule does not refer to direct measurement circuits, which apply to technical installation and physical variable.

In case of single closed regulation circuits, it is divided into 2 parts: regulation part and control part. Regulation part is described in level 1 by process-related installation, and level 2 by the controlled parameter - control part is described by executive device e.

EB - Conditioning of signals related to single drive control. EM - Conditioning of signals related to functional measurement group in digital system. EY - Conditioning of signals related to functional protection group of technical and electrical protection system of the unit. The next counting signs of the circuit does not change when is creating only one combined variable. In case for eg. When creating in DCS systems secondary variables of the same technical installation that differs with counting sign for breakdown level 2, the same rules are to apply as for this variables created from the same installation.

But it is necessary to modificate the counting signs of breakdown level 1 - installation unit code. When technical installations differs only with counting signs of installation it is necessary to assign to a secondary variable counting signs like for one of those installations e.

Calculation of new value on base of 2 variables, e. No sign-up or registration is needed to download signal to noise. There are lots of free fonts to download. Our archive has well over a thousand freeware fonts. Download Free Magazine:Signal To Noise issue 47 pdf files - Free epub, mobi, pdf ebooks download, ebook torrents download.

By anonymous. Can attention be used for top-down control of hearing aids? A short literature review was performed on recent findings on new brain-imaging techniques showing potential for hearing aid control.

Conclusions: Two experiments indicate that it is possible to show improved memory with an experimental noise reduction algorithm at ecological signal-to-noise ratios and that it is possible to replicate these findings in a new language.

The literature indicates that attention-controlled hearing aids may be developed in the future. Furthermore, noise reduction schemes in hearing aids are usually most effective at positive SNRs. Therefore, if one would like to assess outcome of noise reduction schemes at ecological SNRs, testing at positive SNRs is necessary.

However, most conventional speech-in-noise tests are insensitive at those high SNRs because of ceiling effects. Even at high speech performance levels, other factors, such as changes in working memory load, might reveal differences due to the effects of hearing aids on the ease of listening.

Such effects could influence how many words heard in a conversation are remembered. There has been an increase in research investigating how hearing aids can support cognition and hearing and how hearing aids might be controlled by cognition.

Can Hearing Aids Improve Memory? Working memory is important for online language processing in a dialogue. We use it to store, inhibit, or ignore irrelevant information and to perform selected tasks. Working memory is our method of keeping track while taking turns or following the gist of a dialogue. Ng and colleagues introduced a memory recall method that was inspired by Sarampalis, Kalluri, Edwards, and Hafter and Pichora-Fuller The method involved having to recall the last word from each of seven consecutively presented hearing-in-noise test HINT sentences.

Ng et al. The memory recall test assesses both memory and word recognition accuracy. Therefore, any improvement in ease of listening due to hearing aid signal processing would not be revealed by improvements in word recognition accuracy but rather by improvements in recall.

Two experiments were conducted using identical procedures to test memory in different languages Lunner et al. The Danish experiment was designed to replicate the Swedish experiment but in a new language and at a different laboratory. The hypothesis was that the memory test was insensitive to a change from one Scandinavian language to another. The participants in both experiments had moderate symmetrical sensorineural hearing loss and had used well-fitted hearing aids for more than 1 year.

In both experiments, tests were conducted using experimental linear hearing aids with individually shaped frequency responses to ensure audibility of the speech material up to 6. The seven-item memory test was repeated five times in each setting, with both settings tested in counterbalanced order. Thus, the results were obtained in the range of the SNRs observed in the ecological conditions reported by Smeds et al.

In summary, these two experiments indicate that it is possible to show improved memory with an experimental noise reduction algorithm at ecological SNRs and that it is possible to replicate these findings in a different language.