Telephonic communications – Subscriber line or transmission line interface
Patent
1994-10-27
1996-07-09
Hofsass, Jeffery
Telephonic communications
Subscriber line or transmission line interface
379413, 379418, 379400, H04N 908
Patent
active
055352731
DESCRIPTION:
BRIEF SUMMARY
The invention refers to a circuitry for superimposing small, low energy and large, essentially higher energy signals, in particular for transmitting speech signals with a direct signal for the remote supply of a receiving circuit or with a high energy alternating signal, e.g. a call alternating voltage for signaling, with the circuitry including an operational amplifier having one input connected to a pole of a source supplying the small signal and operational voltage inputs connected to a voltage supply source.
Currently, the superimposition e.g. of speech signals and supply voltage is mostly attained with the aid of a transformer, with the e.g. one call alternating voltage being actually supplied in a telephone system via a relay to the subscriber lines. During this time, the speech signal source is completely separated from the subscriber lines. Since transformers as well as relays are relatively large and expensive components and especially relays as mechanical components are highly susceptible to wear, the use of such components results in respective drawbacks.
With the conventional SLIC (subscriber line interface circuit), a solution of this problem is proposed in the manner that the subscriber lines are activated by integrated amplifiers whereby the output voltage area of these amplifiers must contain the entire small and large signal control range of the subscriber line. The switching circuits must therefore be built in accordance with a technology in which the electric strength has to correspond to the greatest occurring signal. Typically, these are 48 V to 60 V for the remote supply and up to 180 V.sub.pp, for the call alternating voltage, whereupon the speech alternating voltage lies in the area of 2-3 V.sub.pp. This realization however results necessarily in the drawback of a very great power loss at the 180 V operational amplifiers whereby the required electric strength necessitates the use of very large transistors so that only very few functions can be integrated on a chip of acceptable dimension.
It is an object of the invention to eliminate these drawbacks and to propose a circuitry of the above-stated type by which the transmission of low energy, weak signals, e.g. speech signals and high energy signals and direct voltages to a subscriber line is possible in a simple manner without requiring transformers and relays and without using especially voltage-stable operational amplifiers.
In accordance with the invention, this is attained by connecting the second pole of the source supplying the low energy signals with the second input of the operational amplifier and by connecting a pole of a source supplying a high energy signal with a pole of the supply voltage source.
These measures make it e.g. possible to control one or both conductors of a subscriber line in a telephone system with operational amplifiers, with its control range and thus also with its supply voltage, which essentially determines the occurring power loss, being suited only to the occurring small signals e.g. the speech signal, and being insulated from the remaining circuitry components such that their supply voltage reference potential can be connected with a source of the high energy signals.
The transmission of the speech signals to the differential voltage inputs of the insulated amplifier or amplifiers may thereby be randomly modulated or unmodulated e.g. capacitively, galvanically or optically, either analog or digital.
For increasing the voltage modulation capability of an operational amplifier, it has also been already proposed to relate the supply voltage to the outlet voltage, with the supply voltage source being linked to the outlet of the operational amplifier.
According to a further feature of the invention, it may be provided to link one pole of the source supplying the high energy signals with an input of the operational amplifier with which also one pole of the supply voltage source is in communication.
These measures result in a very simple structure of the circuitry according to the invention.
Furthermore,
REFERENCES:
patent: 4371840 (1983-02-01), Yokoyama
patent: 4495382 (1985-01-01), Smith et al.
patent: 5396555 (1995-03-01), Shibata et al.
Electronics & Wireless World, vol. 93, No. 1614, 1987, pp. 415-420.
Kausel Wilfried
Kremser Hannes
Stallbaumer Hermann
Winkler Werner
Feiereisen Henry M.
Hofsass Jeffery
Saint-Surin Jacques M.
Semcotec Handelsgesellschaft m.b.H.
LandOfFree
Circuitry for superimposing small, low energy signals and large, does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Circuitry for superimposing small, low energy signals and large,, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circuitry for superimposing small, low energy signals and large, will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1874560