The Traffic Service Position System ( TSPS ) was developed by Bell Labs in Columbus, Ohio to replace traditional cord switchboards . The first TSPS was deployed in Morristown, New Jersey in 1969 and used the Stored Program Control -1A CPU, "Piggyback" twistor memory (a proprietary technology developed by Bell Labs similar to core memory) and Insulated Gate Field Effect Transistor solid state memory devices similar to dynamic random access memory .
35-440: The TSPS system utilized special analog trunks that originated at Class 5 end office circuit switch systems and Class 4 toll access circuit switch systems that were connected to Class 3 primary toll circuit switch systems such as the 4A-ETS/PBC and 4ESS switch systems. The TSPS system did not perform switching between the originating end office switch and the toll switch for the subscriber voice path. The TSPS system included
70-602: A digital modulation method such as ASK, PSK and QAM, i.e. a sinewave modulated by a digital bit-stream, as analog transmission and as an analog signal . Others define that as digital transmission and as a digital signal . Baseband data transmission using line codes , resulting in a pulse train, are always considered as digital transmission , although the source signal may be a digitized analog signal. Analog transmission can be conveyed in many different fashions: There are two basic kinds of analog transmission, both based on how they modulate data to combine an input signal with
105-441: A specific range of frequencies . The audible frequency range for humans is typically given as being between about 20 Hz and 20,000 Hz (20 kHz), though the high frequency limit usually reduces with age. Other species have different hearing ranges. For example, some dog breeds can perceive vibrations up to 60,000 Hz. In many media, such as air, the speed of sound is approximately independent of frequency, so
140-407: A carrier signal. Usually, this carrier signal is of a specific frequency , and data is transmitted through its variations. The two techniques are amplitude modulation (AM), which varies the amplitude of the carrier signal, and frequency modulation (FM), which modulates the frequency of the carrier. Most analog transmissions fall into one of several categories. Telephony and voice communication
175-409: A factor of 2 π . The period (symbol T ) is the interval of time between events, so the period is the reciprocal of the frequency: T = 1/ f . Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals ( sound ), radio waves , and light . For example, if a heart beats at
210-411: A fractional error of Δ f f = 1 2 f T m {\textstyle {\frac {\Delta f}{f}}={\frac {1}{2fT_{\text{m}}}}} where T m {\displaystyle T_{\text{m}}} is the timing interval and f {\displaystyle f} is the measured frequency. This error decreases with frequency, so it
245-465: A frequency of 120 times per minute (2 hertz), the period—the time interval between beats—is half a second (60 seconds divided by 120). For cyclical phenomena such as oscillations , waves , or for examples of simple harmonic motion , the term frequency is defined as the number of cycles or repetitions per unit of time. The conventional symbol for frequency is f or ν (the Greek letter nu )
280-416: A known frequency near the unknown frequency is mixed with the unknown frequency in a nonlinear mixing device such as a diode . This creates a heterodyne or "beat" signal at the difference between the two frequencies. If the two signals are close together in frequency the heterodyne is low enough to be measured by a frequency counter. This process only measures the difference between the unknown frequency and
315-402: A repeating event is accomplished by counting the number of times that event occurs within a specific time period, then dividing the count by the period. For example, if 71 events occur within 15 seconds the frequency is: f = 71 15 s ≈ 4.73 Hz . {\displaystyle f={\frac {71}{15\,{\text{s}}}}\approx 4.73\,{\text{Hz}}.} If
350-519: A signal often has high signal-to-noise ratio and cannot achieve source linearity, or in long distance , high output systems, analog is unattractive due to attenuation problems. Furthermore, as digital techniques continue to be refined, analog systems are increasingly becoming legacy equipment. Recently, some nations, such as the Netherlands, have completely ceased analog transmissions ( analog switch-off ) on certain media, such as television, for
385-430: A toll operator who helped facilitate calls requiring human assistance such as person-to-person, collect, third-party-billed, and hotel billing. The TSPS system supported up to seven "Chief Operator Groups" (COGs) with each COG supporting up to 31 operator consoles. Operator consoles initially used nixie tube displays that were quickly replaced by light-emitting diode displays due to reliability issues. The TSPS system
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#1732791371190420-416: Is a transmission method of conveying information using a continuous signal which varies in amplitude , phase, or some other property in proportion to that information. It could be the transfer of an analog signal , using an analog modulation method such as frequency modulation (FM) or amplitude modulation (AM), or no modulation at all. Some textbooks also consider passband data transmission using
455-435: Is also used. The period T is the time taken to complete one cycle of an oscillation or rotation. The frequency and the period are related by the equation f = 1 T . {\displaystyle f={\frac {1}{T}}.} The term temporal frequency is used to emphasise that the frequency is characterised by the number of occurrences of a repeating event per unit time. The SI unit of frequency
490-495: Is called a radio wave . Likewise, an electromagnetic wave with a frequency higher than 8 × 10 Hz will also be invisible to the human eye; such waves are called ultraviolet (UV) radiation. Even higher-frequency waves are called X-rays , and higher still are gamma rays . All of these waves, from the lowest-frequency radio waves to the highest-frequency gamma rays, are fundamentally the same, and they are all called electromagnetic radiation . They all travel through vacuum at
525-411: Is generally a problem at low frequencies where the number of counts N is small. An old method of measuring the frequency of rotating or vibrating objects is to use a stroboscope . This is an intense repetitively flashing light ( strobe light ) whose frequency can be adjusted with a calibrated timing circuit. The strobe light is pointed at the rotating object and the frequency adjusted up and down. When
560-402: Is red light, 800 THz ( 8 × 10 Hz ) is violet light, and between these (in the range 400–800 THz) are all the other colors of the visible spectrum . An electromagnetic wave with a frequency less than 4 × 10 Hz will be invisible to the human eye; such waves are called infrared (IR) radiation. At even lower frequency, the wave is called a microwave , and at still lower frequencies it
595-493: Is termed rotational frequency , is revolution per minute , abbreviated r/min or rpm. 60 rpm is equivalent to one hertz. As a matter of convenience, longer and slower waves, such as ocean surface waves , are more typically described by wave period rather than frequency. Short and fast waves, like audio and radio, are usually described by their frequency. Some commonly used conversions are listed below: For periodic waves in nondispersive media (that is, media in which
630-641: Is the hertz (Hz), named after the German physicist Heinrich Hertz by the International Electrotechnical Commission in 1930. It was adopted by the CGPM (Conférence générale des poids et mesures) in 1960, officially replacing the previous name, cycle per second (cps). The SI unit for the period, as for all measurements of time, is the second . A traditional unit of frequency used with rotating mechanical devices, where it
665-400: Is the speed of light in vacuum, and this expression becomes f = c λ . {\displaystyle f={\frac {c}{\lambda }}.} When monochromatic waves travel from one medium to another, their frequency remains the same—only their wavelength and speed change. Measurement of frequency can be done in the following ways: Calculating the frequency of
700-626: The Hotel Billing Information System (HoBIS) special feature to provide automated billing of long-distance calls from hotel front desks so guests could be charged for calls made almost immediately prior to their departure. Private Teletype data links were provisioned to large hotels that subscribed to this service. Debuted in Phoenix, Arizona in 1977, the Automated Coin Toll System (ACTS)
735-404: The "Remote Trunking Arrangement" (RTA) feature that consolidated the trunk connection at the originating switch and provided a switched connection to a telephone operator only as required for a short duration at the beginning of a call to obtain billing information or at the end of a call in which the caller requested "time and charges". The TSPS system provided a temporary switched connection to
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#1732791371190770-491: The alternating current in household electrical outlets is 60 Hz (between the tones B ♭ and B; that is, a minor third above the European frequency). The frequency of the ' hum ' in an audio recording can show in which of these general regions the recording was made. Aperiodic frequency is the rate of incidence or occurrence of non- cyclic phenomena, including random processes such as radioactive decay . It
805-421: The frequency of the strobe equals the frequency of the rotating or vibrating object, the object completes one cycle of oscillation and returns to its original position between the flashes of light, so when illuminated by the strobe the object appears stationary. Then the frequency can be read from the calibrated readout on the stroboscope. A downside of this method is that an object rotating at an integer multiple of
840-545: The number of counts is not very large, it is more accurate to measure the time interval for a predetermined number of occurrences, rather than the number of occurrences within a specified time. The latter method introduces a random error into the count of between zero and one count, so on average half a count. This is called gating error and causes an average error in the calculated frequency of Δ f = 1 2 T m {\textstyle \Delta f={\frac {1}{2T_{\text{m}}}}} , or
875-436: The purposes of the government saving money. Frequency Frequency (symbol f ), most often measured in hertz (symbol: Hz), 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 to distinguish it from spatial frequency . Ordinary frequency is related to angular frequency (symbol ω , with SI unit radian per second) by
910-410: The reference frequency. To convert higher frequencies, several stages of heterodyning can be used. Current research is extending this method to infrared and light frequencies ( optical heterodyne detection ). Visible light is an electromagnetic wave , consisting of oscillating electric and magnetic fields traveling through space. The frequency of the wave determines its color: 400 THz ( 4 × 10 Hz)
945-560: The rotation rate of a shaft, mechanical vibrations, or sound waves , can be converted to a repetitive electronic signal by transducers and the signal applied to a frequency counter. As of 2018, frequency counters can cover the range up to about 100 GHz. This represents the limit of direct counting methods; frequencies above this must be measured by indirect methods. Above the range of frequency counters, frequencies of electromagnetic signals are often measured indirectly utilizing heterodyning ( frequency conversion ). A reference signal of
980-414: The same speed (the speed of light), giving them wavelengths inversely proportional to their frequencies. c = f λ , {\displaystyle \displaystyle c=f\lambda ,} where c is the speed of light ( c in vacuum or less in other media), f is the frequency and λ is the wavelength. In dispersive media , such as glass, the speed depends somewhat on frequency, so
1015-461: The strobing frequency will also appear stationary. Higher frequencies are usually measured with a frequency counter . This is an electronic instrument which measures the frequency of an applied repetitive electronic signal and displays the result in hertz on a digital display . It uses digital logic to count the number of cycles during a time interval established by a precision quartz time base. Cyclic processes that are not electrical, such as
1050-473: The wave speed is independent of frequency), frequency has an inverse relationship to the wavelength , λ ( lambda ). Even in dispersive media, the frequency f of a sinusoidal wave is equal to the phase velocity v of the wave divided by the wavelength λ of the wave: f = v λ . {\displaystyle f={\frac {v}{\lambda }}.} In the special case of electromagnetic waves in vacuum , then v = c , where c
1085-419: The wavelength is not quite inversely proportional to frequency. Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances. In general, frequency components of a sound determine its "color", its timbre . When speaking about the frequency (in singular) of a sound, it means the property that most determines its pitch . The frequencies an ear can hear are limited to
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1120-462: The wavelength of the sound waves (distance between repetitions) is approximately inversely proportional to frequency. In Europe , Africa , Australia , southern South America , most of Asia , and Russia , the frequency of the alternating current in household electrical outlets is 50 Hz (close to the tone G), whereas in North America and northern South America, the frequency of
1155-510: Was an addition to TSPS which provided an automated way to perform charge advisory and toll collection of coin paid calls, reducing the need for operator involvement. The ACTS sub-system handled the automated voice announcements, e.g. "Please deposit five cents for the next three minutes" (initially voiced by Jane Barbe , and later Pat Fleet ), and worked with TSPS for coin deposit (start of call) and coin collection/coin return (at end of call). Analog transmission Analog transmission
1190-589: Was originally primarily analog in nature, as was most television and radio transmission. Early telecommunication devices utilized analog-to-digital conversion devices called modulator/demodulators, or modems , to convert analog signals to digital signals and back. The analog transmission method is still very popular, in particular for shorter distances, due to significantly lower costs with complex multiplexing and timing equipment that are unnecessary, and in small "short-haul" systems that simply do not need multiplexed digital transmission. However, in situations where
1225-589: Was replaced by the Operator Service Position System (OSPS) feature package developed for the 5ESS switching system. During the era of TSPS systems, calls to mobile and marine radiotelephone customers were initially handled by operators at a Special Operator Service Treatment cord switchboard. Operator assisted calls to international destinations were handled by "Code 10" and "Code 11" operators generally co-located at special gateway international switching systems. The TSPS system included
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