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Studios and their facilities
Published in Michael Talbot-Smith, Audio Engineer's Reference Book, 2013
Malcolm Nelson, Peter Harris, Larry Goodson, John Howell, Peter Jackson, Geoff Atkins, Yasmin Hashmi, Tim Robinson
The telephone balance unit (TBU) contains an electronic hybrid transformer which takes advantage of the characteristics of the telephone line. The hybrid transformer attempts to adjust automatically to match itself to the characteristic impedance of the telephone line. In the case of a perfect match it would be possible to turn the two wires of the telephone line, which carry speech in both directions, into a four-wire line with separate incoming and outgoing speech circuits. In practice the TBU is not perfect and between 20 and 30 dB of separation may be achieved between the incoming and outgoing speech in a real system. This separation is needed to reduce the coloration of the studio sound by its connection to the telephone line which has to carry the same studio signal to the incoming caller. In order to prevent feedback while the caller is on air the outgoing signal presented to the TBU must be a clean feed (mix-minus) signal that is, it will contain the composite studio output signal after the subtraction of the incoming signal from the telephone line. The TBU is also necessary to provide a barrier between the telephone line, which carries a d.c. voltage, and the mixing desk. In the UK it is also necessary for the TBU to be approved by the BABT (British Approvals Board for Telecommunications) if it is to be connected to the public switched telephone network (PSTN).
Studios and their facilities
Published in Michael Talbot-Smith, Audio Engineer's Reference Book, 2012
The telephone balance unit (TBU) contains an electronic hybrid transformer which takes advantage of the characteristics of the telephone line. The hybrid transformer attempts to adjust automatically to match itself to the characteristic impedance of the telephone line. In the case of a perfect match it would be possible to turn the two wires of the telephone line, which carry speech in both directions, into a four-wire line with separate incoming and outgoing speech circuits. In practice the TBU is not perfect and between 20 and 30 dB of separation may be achieved between the incoming and outgoing speech in a real system. This separation is needed to reduce the coloration of the studio sound by its connection to the telephone line which has to carry the same studio signal to the incoming caller. In order to prevent feedback while the caller is on air the outgoing signal presented to the TBU must be a clean feed (mix-minus) signal that is, it will contain the composite studio output signal after the subtraction of the incoming signal from the telephone line. The TBU is also necessary to provide a barrier between the telephone line, which carries a d.c. voltage, and the mixing desk. In the UK it is also necessary for the TBU to be approved by the BABT (British Approvals Board for Telecommunications) if it is to be connected to the public switched telephone network (PSTN).
Crystal Filters
Published in John T. Taylor, Qiuting Huang, CRC Handbook of ELECTRICAL FILTERS, 2020
A critical component in discrete-crystal filters is the RF transformer which is required for the hybrid lattice circuit. This “hybrid transformer” must be linear and stable and tightly balanced. At frequencies above 1 MHz these transformers are typically bifilar wound on powdered iron, toroid cores. Care must be taken to reduce the distributed capacitance as much as possible by carefully spreading the windings on the core. Because the filters are typically fairly high impedance circuits, the losses in the transformers must be kept to an absolute minimum. Most discrete-crystal filters are packaged in hermetically sealed cases primarily to protect the transformers from moisture and dirt.
Design of a Hybrid Transformer based on an Indirect Matrix Converter for Distribution Networks
Published in Electric Power Components and Systems, 2022
Mahmoud Fereydouni, Esmaeel Rokrok, Shamsodin Taheri
A hybrid transformer (HT) can offer an immediate solution to mitigate these limitations. In [10] a HT based on a direct matrix converter (DMC) as a smart transformer was presented. In this study, the converter has a variable switching frequency due to the hysteresis modulation method, which increases the switching losses and challenges the design of the input and output filters. In [8, 11] multiple alternative configurations were developed using power electronic converters. In [12], a HT was studied based on back-to-back converters in the presence of a DC-link capacitor. Although a comprehensive control system was described, the system reliability is low due to the existence of the DC- link capacitor. In [13], a HT based on a DMC without access to the virtual DC link based on the variable modulator frequency was presented in which the variable switching frequency challenges the design of the converter input and output filters.
Investigation of Dielectric Strength of Transformer Oil Based on Hybrid TiO2/Al2O3/MoS2 Nanofluid Using Taguchi and Response Surface Methodology
Published in IETE Journal of Research, 2021
S. Sumathi, R. Rajesh, P. Subburaj
On the basis of the L16 Taguchi orthogonal array design matrix, 16 experimental tests were conducted on the nano hybrid transformer oil, and the S/N ratio has been computed for the dielectric strength of the 16 trials in the Taguchi orthogonal array design matrix, as shown in Table 3. Each trial was carried out five times and the mean value was reported to maintain accuracy.