Wave transmission lines and networks – Automatically controlled systems – With control of equalizer and/or delay network
Patent
1982-12-06
1985-09-03
Rubinson, Gene Z.
Wave transmission lines and networks
Automatically controlled systems
With control of equalizer and/or delay network
179 77, 333119, 323355, H04B 158, H04M 1900
Patent
active
045394431
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a direct current magnetized hydrid transformer adapted for being included in a telephone repeater and connected between a two-wire line and the repeater to provide a transfer between the two-wire and four-wire circuits in the repeater. More particularly, the invention relates to a hybrid transformer adapted for use in repeaters, and adapted for being used to transform analogue telephone signals coming from a line into PCM-coded signals and vice versa.
BACKGROUND
For converting analogue telephone signals from a particular subscriber across a particular line, repeaters are used to provide two different signal paths. In one of these paths the analogue signals are coded to the PCM-coded signals and in the other a decoding of the digital PCM-coded signal flow is carried out. Furthermore, amplifiers are used to compensate for the attenuation of the line. It is also known to use a direct current magnetized hydrid transformer for dividing the input of a repeater towards the two-wire line, the transformer feeding the desired current to the subscriber's set connected to the line. At the same time, a DC-magnetizing of the transformer core is obtained.
SUMMARY OF INVENTION
For constructing transformer hydrids included in repeaters, there are certain requirements regarding the design of the hybrid and consideration must be given to the DC-magnetizing of the transformer. Firstly, the input terminals on the two-wire side should be balanced to a ground point, since otherwise so-called longitudinal currents arise across the line. Secondly, a balance impedance should be connected to the transformer so that the impedance as seen from the hybrid towards the two-wire side can be balanced out; i.e., an impedance match is to be achieved to the incoming line. Finally, the echo attenuation on the two-wire side has to be high for impedances (i.e., line and subscriber's set impedances) which are connected to the two-wire side of the hybrid. Otherwise reflections arise across the line between the hybrid and the subscriber's set.
In addition, there may be problems in connection with a DC-magnetized hydrid transformer to preventing incoming speech voltages from being short-circuited via the current loop through which direct current is supplied from a battery towards the associated line. Current supply has previously been provided via current transformers with high output impedance or else a choke has been connected in series with the associated direct current source (see attached FIGS. 2 and 3 discussed below). Especially for a DC-magnetized hybrid transformer, there are certain requirements for the current durability of the core material (i.e., in order to obtain the desired inductance, the direct current should have a certain value for obtaining the transformer function).
In accordance with the invention the above-mentioned problems are solved by dividing the two primary windings at the line side of the hybrid into two winding parts each, and by connecting the feeding voltage source, which primarily will supply the subscriber with direct current, to the common connection point between the two winding parts. More particularly, in accordance with the invention there is provided a direct current magnetized hybrid transformer adapted for being included in a repeater for a telephone line to provide a two-wire to four-wire coupling. The line is known to have a determinable impedance. The transformer comprises a first primary winding and a first pair of secondary windings magnetically coupled thereto. There is also included a second primary winding with a second pair of secondary windings being magnetically coupled thereto. The secondary windings create a four-wire path. At least one winding from each pair is connected to a balancing impedance which is matched to the line impedance. The first and secondary primary windings each include two winding parts, each having a respective number of turns such that the number of turns of one of said winding parts is in a determined relationshi
REFERENCES:
patent: 2854514 (1958-09-01), Ensink et al.
patent: 3959718 (1976-05-01), Hasegawa
patent: 4110636 (1978-08-01), Dijkmans
patent: 4197431 (1980-04-01), Vis
patent: 4234763 (1980-11-01), Dijkmans et al.
patent: 4297536 (1981-10-01), Buchner
Rubinson Gene Z.
Telefonaktiebolaget LM Ericsson
Vaas R.
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