Telephone Set Research Articles

A new artificial ear for telephone measurements

Opinion tests show the importance of the acoustical leakage between the handset and the human ear for the subjective speech transmission quality of telephone sets. Artificial ears, which are now used for telephone measurements, do not allow measurements with variable leakage. Using an artificial ear formed as an individual human ear does not lead to reproducible results. Both problems are avoided by this new ear. It has a simplified shape, which is determined by only a few geometrical parameters. Thus the transmission characteristics can be described by a mathematical model. Nevertheless it approximates a human ear, referring to the dependence of the leakage and the transmission characteristics on the force applied to the handset. Measurements using the artificial ear are reproducible and show high conformity with measurements of handsets at human ears. Implemented in an artificial head, the ear can also be used to measure hands‐free telephones. The directional characteristics of the artificial ear in a f...

Review Of Cadmium In Plastic Waste In Sweden

Cadmium containing stabilizers are used only in certain polyvinylchloride (PVC) products for special weather, light or temperature resistance. The total consumption of cadmium used as a chemical stabilizer in Sweden is expected to be about 1.5 tonnes/year in 1991-1992, while the amount in pigments is approximated to be 6 tonnes/year. It is determined that most of the cadmium that enters into the combustible fraction of municipal solid waste (MSW) comes from plastics and pigments in various products. Acrylonitrile Butadiene Styrene copolymers (ABS) products are the main source of plastics contained cadmium pigments. These products are usually consumer electronics such as television and telephone sets, computer, radios, etc. In practice, it is very difficult for a country like Sweden to act alone and implement regulations for cadmium due to international trade and heavy import/export of products. There is no doubt that the transition period to adopt other alternatives, as requested by the Swedish Cadmium Ordinance, takes time and a flow of cadmium from plastic wastes into landfills and incinerators is expected during the coming years. This is also due to the long lifetime of some plastic products which contain cadmium. Continuous and consistent monitoring of cadmium in landfills and incineration plants is required in order to be able to evaluate the effect of the Ordinance on cadmium.

Review of Cadmium in Plastic Waste in Sweden

Cadmium containing stabilizers are used only in certain polyvinylchloride (PVC) products for special weather, light or temperature resistance. The total consumption of cadmium used as a chemical stabilizer in Sweden is expected to be about 1.5 tonnes/year in 1991-1992, while the amount in pigments is approximated to be 6 tonnes/year. It is determined that most of the cadmium that enters into the combustible fraction of municipal solid waste (MSW) comes from plastics and pigments in various products. Acrylonitrile Butadiene Styrene copolymers (ABS) products are the main source of plastics contained cadmium pigments. These products are usually consumer electronics such as television and telephone sets, computer, radios, etc. In practice, it is very difficult for a country like Sweden to act alone and implement regulations for cadmium due to international trade and heavy import/export of products. There is no doubt that the transition period to adopt other alternatives, as requested by the Swedish Cadmium Ordinance, takes time and a flow of cadmium from plastic wastes into landfills and incinerators is expected during the coming years. This is also due to the long lifetime of some plastic products which contain cadmium. Continuous and consistent monitoring of cadmium in landfills and incineration plants is required in order to be able to evaluate the effect of the Ordinance on cadmium.

Analog blocks in telecommunications systems

Monolithic realizations of general telecommunications systems require high-performance internal circuits. To achieve these results digital and analog solutions are available. The general trend is toward digital implementations which guarantee high density and easy design. However, in each overall system there are some blocks requiring necessary an analog solution. Furthermore the entire system performance is often strictly dependent on the performance of the analog section. In this paper the role of analog blocks in three telecommunications systems (ISDN, line card and telephone set) is described.

Can the VLSI technology meet the needs of acoustic echo control system?

Since the introduction of hands-free telephone sets, acoustic echo cancellation has been a challenge for engineers. While in the past the problem was overridden using gain switching techniques, recently many authors have shown that the best solution for the echo compensation problem is represented by an adaptive filter which iteratively tries to identify the unknown impulse response of the system loudspeaker-room-microphone. Unfortunately the VLSI technology was not suitable to meet the requirements of this solution in a single chip acoustic echo canceller. The present paper, starting from a CMOS 1.2μm technology, will show some figures in terms of speed and silicon area taken for some basic blocks (such as adders, multipliers, memories) required by a canonical solution based on an adaptive FIR filter of 1000 taps with coefficients updated by the NLMS algorithm. Moreover, it will be shown a more efficient solution for the acoustic echo compensation based on a sub-bands approach. Simulated experiments with this architecture will be presented, compared with the ones of the canonical solution for what concerns size, number of operations required and performances.

Accessory communication device for telephone sets

An accessory communication device for telephone sets includes: a wearer's harness member made of a flexible material for being manipulated to be worn around a user's neck; a pair of earphone arrangements each having a flexible cord and a connector provided thereto detachably held at the opposing sides of the wearer's harness member for being comfortably positioned in a user's ears; and a transmitting fixture having electric circuits and connecting members respectively disposed therein for making electrical connections with the earphone arrangements and a telephone set so as to effect communication transmitting and receiving operations therewith.

A new prevention against the disturbance by narrow-band signal in hands-free telephone set with compact echo cancellers

A new prevention against the disturbance by narrow-band signal in hands-free telephone set with compact echo cancellers

High density pin board matrix switches for automated MDF systems

High-density, low-cost pin board matrix switches for automated main distributing frame (MDF) systems are described. The MDF system has two basic functions, cross connection and route setting for line test functions. These two functions can be performed automatically using a robot hand to insert a connecting pin into a crosspoint hole on the matrix board. Each crosspoint hole has four isolated cylindrical contacts that are connected to X/sub A/, Y/sub A/, X/sub B/, and Y/sub B/ conductive patterns, which represent the A and B wires of a telephone set circuit. Corresponding to the four contacts of a crosspoint hole, a connecting pin has two spring contacts, one spring contact to connect X/sub A/ and Y/sub A/ conductive patterns, and the other for connecting X/sub B/ and Y/sub B/ conductive patterns. In addition, arrangements have been made to perform the route setting for line testing. A matrix board with crosspoint holes on a 1.5-mm grid has been attained using the low-contact-force design and minimum insulation spacing between the neighboring conductive patterns. The design also considers requirements for the robot hand interface. These pin board matrix switches allow the MDF system to be automated. >

Studies of the speech transducing performance of carbon and electret telephone transmitters

Five studies examined the relative performance of traditional carbon-type telephone transmitters and newer electret-type transmitters that have come to replace the carbon-type in contemporary telephone set designs. Focus is on the validity of the transmit objective loudness rating (TOLR) metric as a predictor of transmitter efficiency in response to real speech input. TOLR is the IEEE recommended metric (IEEE Standard 269-1983) for objectively characterizing the efficiency with which telephone transmitters convert acoustic energy to electric energy. These studies indicate that the relationship between TOLR and transmitter efficiency for real speech is not the same for carbon and electret transmitters. Relative to what is observed with carbon transmitters, TOLR was shown to underpredict the real speech efficiency of electret transmitters by approximately 3 dB. Two mechanisms are involved in this effect. First, carbon transmitters have a lower peak-clipping, or compression, threshold than electret transmitters. This difference is not accounted for in the measurement of TOLR where the input signal consists of a swept sine wave whose constant amplitude (sound-pressure level of 88 dB) is below the compression threshold of carbon transmitters. Second, the efficiency of carbon transmitters, but not electret transmitters, declines during the first minutes after the telephone handset is taken off-hook. The formal TOLR measurement protocol overestimates carbon transmitter efficiency because the transmitter is characterized immediately after being taken off-hook, not over a broader period of time which would be more predictive of its efficiency in real use. These results have implications for the choice of TOLR design objectives for electret transmitter telephone sets. The greater relative efficiency of electret transmitters for real speech input also needs to be considered when grade-of-service models, which now assume the use of carbon transmitter telephone sets, are used to estimate the transmission quality of network connections.

Unified alignment of isdn-relevant information communications services/applications through a cubic framework

A cubic (three-dimensional) framework is proposed for mapping various information communications services. The framework implies the important aspect of information technology (IT), or C&C (integration of computers and communications) technology as follows. The first axis is based upon the service classification made for BISDN-relevant services by the CCITT. This ‘communications’ axis covers not only the simple communication, or ‘space-wise information transfer’, but also messaging, retrieval etc. as ‘the combined space/time-wise information transfer’. The second axis represents ‘the multiplicity of media use’ in the human interface of information handling systems. The third axis represents the extent of ‘information processing/conversion’ or the level of computer technology penetration. In the latter part of this paper, the important interrelations between computer communications services and ISDN deployment are discussed using the scope of the above-proposed cubic map. The penetration of PMI (personal machine intelligence) to the same level as telephone set and television set, and the corresponding computer communications services requirements are identified as a fundamental driving force of (N)ISDN deployment.

The effects of mobile telephoning on driving performance

The effects of telephoning while driving were studied in three different traffic conditions, i.e. in light traffic on a quiet motorway, in heavy traffic on a four-lane ring-road, and in city traffic. Twelve subjects, unfamiliar with mobile telephones, drove an instrumented vehicle for one hour each day during three weeks and while in each of the three traffic conditions, had to operate the mobile telephone for a short while. To ensure a fixed “heavy traffic load” in the second condition, the subjects were instructed to follow another instrumented vehicle (at a safe distance). The results showed a significant effect of telephoning while driving as opposed to normal driving (i.e., not involving telephone conversation), on the effort subjectively measured by an effort scale and objectively measured by heartrate indices and on some of the measured parameters of driving performance. One half of the subjects had to operate the telephone manually, the other half performed the telephone task with a handsfree mobile telephone set. The subjects who operated the handsfree telephone showed better control over the test vehicle than the subjects who operated the handheld telephone, as measured by the steering wheel movements. Also, a clear improvement over time in the course of the 15 test days was found for some of the measurements. As a consequence of the results, some advice concerning mobile telephoning can be given to authorities, manufacturers, and users.

DPCM coding of spectral amplitudes without positive slope overload

The author considers the problem of coding the spectral amplitudes of a sinusoidal transform coding (STC) vocoder operating at 2400 b/s, which was previously considered by R.J. McAulay and T.F. Quatieri (1987). Differential pulse code modulation (DPCM) coding of spectral amplitudes in vocoders can cause formant clipping because of positive slope overload. The author presents a modified DPCM coder that prevents positive slope overload by anticipating large spectral peaks. When the vocoder is used on speech taken from a standard telephone set, a time-varying distortion of the low-end frequencies is observed. When the modified DPCM coder is applied to the telephone-set speech, its success was obvious. The time-varying distortion of the low-end frequencies is eliminated. Performance of the STC vocoder on the telephone-set speech is essentially identical to its performance on flat-frequency-response speech.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

ISDN telephone sets with advanced voice functions

Three types of ISDN (integrated services digital network) telephones and LSIs for ISDN telephones have been developed. These telephones feature improved functions using network information and ciphered voice communication using an end-to-end digital link. A low-cost network interface sector that uses LSI with layer 1 to 3 control functions and related software is incorporated. Also, an analog I/O sector was incorporated together with a codec onto a single chip. Low-power-consumption designs for all circuits enable operation with line-fed power for a telephone set, thereby securing communication in times of emergency. >

Metal oxide on the surface of contacts having excellent contact performance

AbstractPreviously, a substance identified as ammonium sulfate was found on the speech path contacts of XS‐type crossbar switches in the electronic switching system of NTT. On the basis of this finding, the contacts of 99% Au/1 % Ni alloy in contact with Pd were developed by the author's group more than ten years ago for the pushbutton dial contacts of telephone sets. These contacts showed excellent performance and are still in use at the present. This development depends on the hypothesis that some metal oxides have the effect of preserving contact performance against the influence of air pollution.In this paper, the hypothesis, experimental results in the investigation of the properties of the Au‐Ni alloy surface, and applications of this alloy for electrical contacts are described. The experimental results are as follows: by heating the Au‐Ni (Ni 1%) alloy, it was confirmed that nickel oxide was accumulated on the alloy surface; by measuring the contact angle of a water droplet on the Au‐Ni alloy, the relationship between the angle and accumulation of nickel oxide was obtained; and by operating the contacts combined with Au−1 % Ni and Pd which are similar to the actual use of contacts, the characteristics and the size of the formed powder were evaluated.

4972187 Numeric encoding method and apparatus for neural networks

This paper presents an approach for acquiring digitized ECG samples in a personal computer using an offline communication technique. For this, two standalone embedded modules are placed at the two ends of the communication link. The transmit end module collects ECG samples from the source and stores them in a RAM. Finally it converts each data byte into a bi-phase encoded bit stream for transmission using a standard telephone set through post office telephone line. The receive-end module, coupled with the telephone receiver decodes the ECG data, and then delivers them to a desktop computer through the serial port. An application software in the computer is used to store these samples for visual inspection. The detailed architecture and test results are discussed with synthetic ECG data available from PTB diagnostic ECG database (ptb-db) under Physionet.

Hearing assist telephone

First Page

Hands‐free telephone using compact echo cancelers and voice‐switched attenuators

An all‐in‐one type hands‐free telephone set was constructed by using a single chip digital signal processor integrated circuit (DSP IC). It includes a compact acoustic echo canceler, a sidetone echo canceler, and voice‐swilched variable attenuators. An echo canceler whose length is only 16 ms (128 taps for an 8‐kHz sampling) can suppress the power of an impulse response of the loudspeaker‐microphone acoustic coupling path by more than 15 dB, because the major part of the path for an all‐in‐one telephone set is due to short direct paths. Most of the sidetone can also be suppressed by more than 20 dB by using an echo canceler of 8‐ms length. A speech circuit including these echo cancelers and conventional voice‐switched variable attenuators was composed of only one medium‐performance DSP IC (75‐ns machine cycle, 2K words of ROM and 512 words of RAM, and an additional 1000 ASIC gates}, CODEC IC's, and a few analog IC's. Complete simultaneous conversation is feasible with this hands‐free telephone circuit because the voice‐switched attenuation could be reduced to 10 dB or less.

Loudspeaking telephone set having an anti‐Larsen device for instability detection and control

A loudspeaking telephone set incorporating an anti-Larsen device which upon detecting instability controls the insertion of an attenuator in either or both of the listening and transmission channels. Such device incorporates a detection circuit (6) for detecting a start of instability, consisting of two analogue multiplier circuits (11), (15), two low-pass filters (18), (20), and two absolute-value convertors (19), (21), these elements being arranged in two parallel chains. One of the multiplier circuits (11) receives at its inputs the amplified signal from the receiver (4) and from the microphone (3). The other multiplier circuit (15) receives the same signals, except that one of them is phase-shifted approximately 90 DEG at the Larsen frequency, by a phase-shift circuit (16). At the output of the absolute-value convertors (19), (21), the signals are added together by an adder (23) which delivers at its output an attenuation control signal after passing through a threshold comparator (24). From among all the signals present in the telephone set, the detection circuit (6) performs effective selection of those which correspond to a start of instability.

Apparatus in a loudspeaking telephone set for supplying power to an amplifier connected to the loudspeaker

Apparatus for powering a loudspeaker amplifier (5) in a telephone set fed with a line current (ILO) from a telephone line (3). An incomming speech signal (S) is amplified (8) and sent to a loudspeaker (4) via the amplifier (5), which is powered via its feed connections (19, 20) from a reservoir capacitor (6). By the capacitor feed there are avoided variations in the line current (ILO) on amplification of the speech signal (S). The capacitor is recharged with the aid of the speech circuit (13), which has an amplifier means (16, 17) sensing a line voltage (UO) via a voltage sensing circuit (18). The amplifier means (16, 17) steers the line current (ILO) to a constant value responsive to the line voltage (UO) by sending a current (16) to the line (3) via a resisitor (R1), thus keeping constant a current (14) through the resistor (R1), this current being sensed by the ampifier means. The reservoir capacitor (6) is connected via a controllable current generator (22) to the resistor (R1) and a circuit (24), which senses the voltage across the resistor (R1) and controls the generator (22). The reservoir capacitor (6) is charged by a current (15) through the current generator (22) and the amplifier means (16, 17) controls its output current (16) such that the current (14 = 15 + 16) through the resistor (R1) is kept constant. The apparatus utilizes the existing speech circuit (13) to keep the line current (ILO) constant at the power supply.

New pay phones hit the street

The sweeping change in public telephony that is resulting from a 1984 Federal Communications Commission (FCC) decision to open the US pay telephone market to competition is examined. Consumers are already confronted with a variety of telephone sets, services, operators, and, perhaps most important, rates. Soon equipment made by many different manufacturers will let users send voice, data, and facsimile messages through public terminals. the differences between private pay phones (PPPs) and the local-exchange carriers' phones are discussed. Unlike the traditional phones, which rely on facilities of the telephone company for many functions, including rate computation, credit card verification, connection of collect calls, generation of operator messages, prompts, and tones, PPPs must perform all of these functions-and more-by themselves, typically through the use of dedicated 8-bit microprocessors and custom software. Competition in the industry and the question of how best to regulate the PPP industry, particularly as regards rate, are considered. The potential impact of ISDN is briefly examined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>