US1992833A - Two-way telephone and like electrical system - Google Patents

Two-way telephone and like electrical system Download PDF

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Publication number
US1992833A
US1992833A US690320A US69032033A US1992833A US 1992833 A US1992833 A US 1992833A US 690320 A US690320 A US 690320A US 69032033 A US69032033 A US 69032033A US 1992833 A US1992833 A US 1992833A
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United States
Prior art keywords
amplifier
receiving
coil set
speech
hybrid coil
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Expired - Lifetime
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US690320A
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English (en)
Inventor
Murphy Francis Money Graham
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RCA Corp
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RCA Corp
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Publication date
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other

Definitions

  • This invention relates to two-way telephone and like electrical signalling systems and has for its object to provide a two-way system suitable line through the usual hybridcoil set.
  • an ideal hybrid coil set would be one in whichthe balance was so perfect that there would be no interaction between the receiving and transmitting channels while the loss between either of these channels and the subscribers line was a minimum.
  • Accurate balance in a hybrid coil set involves that the impedance of the subscribers line shall be accurately simulated at all frequencies employed, and since, in the majority of practical cases,the subscribers line is apt to be changed from time to time (c. g.
  • the subscribers line in use at any time may be any of a plurality of lines'leading to differently situated subscribers) .thesaid simulation cannot be more than approximate and therefore some out-of-balance will in practice almost always exist.
  • blocking devices which are controlled in operation by the speech or other signal currents, may take any of a variety of different forms one of the most usual arrangements being that in which normally (i. e. in the absence of speech) the transmitting channel is paralyzed (i. e. inoperative) and the receiving channel made (i. e.
  • Figure 2 illustrates a modification of the system of Figure 1 in accordance with the principles of the present invention
  • Figure 3 illustrates in some detail a desirable feature of the invention
  • Figure 4 which is shown in parts 4a, 4b, 4c, illustrates a practical embodiment of the invention.
  • the subscribers line L is associated through the usual hybrid coil set H with a transmitting channel and with a receiving channel.
  • a switch or contact device D whereby said channel may be opened or closed i. e. disconnected from or connected to the radio or other transmitter proper, while the receiving channel leads from the radio or other receiver proper may be connected through a switch or contact device E and then through the receiving amplifier G to the hybrid coil set.
  • a blocking amplifier detector unit A is connected to receive its in- 4 input is energized from a point between the input terminals of the receiving amplifier G and the contact device E in the receiving channel.
  • the noise level at the input terminals of the receiving amplifier G is r and that the gain of the receiving amplifier may be expressed by a power ratio g.
  • the loss in energy in passing from the receiving channel side of the hybrid coil set H through the said set to the transmitting channel may be expressed by a power ratio It and that when speech to be transmitted comes from the subscribers line the energy thereof may be expressed by the quantity t.
  • speech from the subscribers line will cause equal E. M. F.s in both the transmitting, and receiving channels but no E. M. F.
  • the input energy to the blocking amplifier detector may be expressed by r g h' (ignoring the noise from the subscribers line).
  • the principal object of the present invention is to render the necessary adjustments less critical and this object is achieved according to the main feature thereof by taking one of the energies which are to be difierentially utilized for the control of the blocking device from the receiving channel side of the hybrid coil set instead of from the transmitting channel side thereof.
  • the energy level at the input terminals of the blocking amplifier detector will be r X g and, when speech from the subscribers line arrives, the energy level at the said input terminals will be r +t.
  • the margin for operation is therefore still i but the necessary adjustment is less critical since it is now only necessary to adjust for a balance of the effects of TX g and r.
  • the practical importance of this improvement will be realized from the fact that when only the impedance of the subscribers line is changed, e. g. when the hybrid coil set is changed over from one subscriber to another both the value of h is changed and the value of the impedance facing the output terminals of the receiving magnifier is changed, i. e. the apparent gain of the receiving amplifier is changed.
  • a second feature of the invention is concerned with the means for differentially utilizing the two energies for control of the blocking device and, according to the said second feature, instead of employing a gain controlling amplifier detector to control the gain of the blocking amplifier detector the outputs from two correspondingly energizedamplifier detectors are differentially combined and the combined energy utilized to control the blocking device.
  • the output from an amplifier A--whose input terminals are energized either (and preferably) from the receiving channel side of the hybrid coil set (as is the device A of Figure 2) or from the other side of the hybrid coil set (as is the device A of Figure l) is passed through a transformer T1 one of whose secondary terminals is connected to the grid and anode of a triode V1 the other secondary terminal being connected'through a time control circuit, consisting of a resistance R1 and condenser C1 in shunt, to the cathode'of the triode.
  • the output terminals of an amplifier B whose input terminals are connected to the input terminals of the receiving amplifier are connected to the primary of a second transformer T2 whose secondary terminals are associated with a second triode V2 and a time control circuit C2, B2 in the same way as are the secondary terminals of the first transformer.
  • the cathodes of the two triodes are connected together and connections are taken from the grid and cathode respectively of a third triode V3 to the ends (remote from the cathodes) of the re sistances R1 and R2.
  • the anode and cathode of the triode Vx' are connected together through the usual anode battery HT in series with a resistance R3 shunting a condenser C3.
  • This voltage is utilized in any convenient way (and after direct current amplificaton if required) to control the blocking device C3.
  • the connections between the grid and cathode of third triode and the appropriate resistances in the time control circuits are made, not as above stated and as shown to the ends of these resistance, but to adjustable tapping points thereon the condensers in the two time control circuits being connected between the appropriate cathodes and the appropriate tapping points.
  • the time constants of the two circuits which have been above described as time control circuits are much smaller than the time constant which will, of coursabe given by the resistance-condenser combination C3, R3 in the plate circuit of the triode V3.
  • control circuits can, if desired, be arranged to be adjustable as to their time constants.
  • FIG. 4 of the accompanying drawings which is shown in three parts, namely 4a, 4.2), and do, illustrates in some detail a practical embodiment of the invention, said embodiment being in sheet an arrangement of the type illustrated in Figure l, but incorporating the principal feature of the arrangement shown in Figure 3.
  • a radio receiver (not shown) is connected through a suitable filter illustrated within the dotted rectangle F to the input circuit of a device shown within the dotted rectangle GE ( Figure 40) this device consisting in effect of the receiving amplifier G and of the switch E of Figure 1.
  • the switch action of the device GE is obtained by altering the bias fed to the two pushpull connected valves which constitute the first stage of the said device GE, this bias being altered in manner to be described later by potential fed over the wire Y.
  • the interposition of the amplifier AMP prevents any speech currents from the line L reaching the filter F leading to the apparatus (3C1.
  • the other side of the hybrid coil set H is connected through suitable filter F to the input terminals of a device shown within the dotted rectangle DA said device constituting in efiect the switch D of Figure 1 and an amplifier.
  • the switch action of the device DA is obtained in manner analogous to that in which it is obtained in the deviceGE by alterirx the bias upon the push-pull connected valves constituting the first stage of the said device DA, the bias potential for these valves being fed over the line X.
  • the output from the device DA is taken to the radio transmitter (notshown). Energy from a point intermediate the amplifier AMP and the output terminals of the device GE is passed through a suitable filter F and a suitable variable attenuation device indicated within the rectangle GC1 to the input terminals of the apparatus indicated at BB.
  • this apparatus consists of two single valve stages of amplification in cascade followed by a pushpull connected stage which feeds through a transformer T2 to two valves V2 arranged to act as diodes.
  • the valves V2 are so connected together that they act as a full wave rectifier, the rectified output passing through a time control circuit consisting of a resistance R2 shunted by a condenser C2.
  • the transformer T2 valves V2 resistance R2 and condenser C2 are analogous to the transformer T2 valve V2 resistance R2 and condenser C2 of Figure 3, the amplifier portion preceding the transformer T2 being analogous to thedevice B of Figure 3.
  • the transformer T1 valves V1 resistance R1 and condenser C1 are analogous to the transformer T1 valve V1 resistances R1 and condenser C1 of Figure 3 the stages of amplification within the rectangle AA preceding the transformer T1 being analogous to the device A. Tapping points upon the resistance R1 and R2 are connectedin effect to the grid and cathode respectively of the first valve of 'a two valve arrangement shown within the rectangle CV3 the apparatus within this rectangle being analogous to the valve V3 of Figure 3 plus the apparatus at C (which is not shown in Fig. 3).
  • the cathodes of the valves V1 and V2 are all connected together and as will be obvious from Figure 4 the connections are such that differential control of the unit CV3 is obtained from the voltages set up in the resistance R1 and R2. Connection is taken from the plate of the first valve in the unit CV3 to the effective centre point of the push-pull grid circuit of the first pushpull connected ampliher of the apparatus at GE, and, similarly, connection is taken from the plate of the second valve at CV3 to the effective centre point of the pushpull grid circuit of the first push-pull connected amplifier of the apparatus at DA.
  • connections Y and X respectively arethe connections for feeding the controlling bias potentials to the devices at GE and DA respectively so as to cause these devices to give the required switch actions.
  • the rectangle PU encloses a potentiometer unit from which steady grid and anode potentials are tapped for the various valves as indicated.
  • the apparatus of Figure 4. includes another unit not included in the schematic representations of Figures 1 and 3 said unit being indicated at Z of Figure 4b.
  • the unit Z receives energy from the input terminals of the variable attenuation device CTCl inserted in the path to the input terminals of the device BB and the said device Z supplies control grid bias via the lead GB to the first valve of the apparatus at AA.
  • the apparatus at Z is such as to provide when actuated, an output potential sufficient to bias the first valve of the apparatus at AA to the cut off point, the said apparaus at Z being further so designed that it is actuated by received speech level but not by received noise level so that when speech output comes from the device GE the device Z renders the device AA inoperative but mere noise from the device GE will not cause the device Z to render the device AA inoperative.
  • the apparatus at Z forms the subject of another patent application and no claim is made in this specification to the said apparatus per se.
  • the apparatus at Z sharply difierentiates between received noise level and received speech.
  • This device is preferably provided with a time control circuit whereby the time of restoration of the device may be regulated and the time of restoration should be made long to serve as a hang-over for weak syllables and echo effects
  • Figure 4 shows also a quantity of detail apparatus well known per se, such for example as testing jacks, meters and so forth, but it is not thought necessary to describe this apparatus in the present specification since it has nothing to do with the present invention as such.
  • a two-Way telephone or like electrical signalling system suitable for use for example as a terminal equipment in a two-way radio telephone system and comprising a normally paralyzed transmitting channel, a normally made receiving channel including a receiving amplifier, a hy brid coil set or its equivalent for associating the input terminals of the transmitting channel and the output terminals of the receiving amplifier with a subscribers line, an amplifier detector connected to receive its input at a point between said hybrid coil set and the output terminals of said receiving amplifier, a second amplifier detector whose input terminals are energized from a point between the input terminals of the receiving amplifier and the point at which the normally made receiving channel may be paralyzed, connections between said second and first mentioned amplifier detectors whereby said second mentioned amplifier detector controls the gain of the first in dependence upon the input to said second amplifier detector and a blocking device energised in dependence upon the output of the first mentioned amplifier detector for making the transmitting channel and paralyzing the receiving channel.
  • a two-way telephone or like electrical signalling system suitable for use, for example as a terminal equipment of a two-way radio telephone system and comprising a normally paralyzed transmitting channel, a normally made receiving channel including a receiving amplifier, a hybrid coil set or its equivalent for associating the input terminals or" the transmitting channel and the output terminals of the receiving amplifier with a subscribers line, an amplifier connected to receive its input at a point between said hybrid coil set and the output terminals of said receiving amplifier, a second amplifier whose input terminals are energized from a point between the input terminals of the receiving amplifier and the point at which the normally made receiving channel be paralyzed, rectifiers energized from the outputs of each of said last menticned amplifiers, a. further amplifier connected to be differentially controlled in dependence upon the voltage outputs from the two said rectifiers, and means for utilizing the output from said further amplifier to make the normally paralyzed transmitting channel and paralyze the normally made receiving channel.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Noise Elimination (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Interface Circuits In Exchanges (AREA)
  • Near-Field Transmission Systems (AREA)
US690320A 1932-09-03 1933-09-21 Two-way telephone and like electrical system Expired - Lifetime US1992833A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB24631/32A GB408300A (en) 1932-09-03 1932-09-03 Improvements in or relating to two-way telephone and like electrical systems

Publications (1)

Publication Number Publication Date
US1992833A true US1992833A (en) 1935-02-26

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Application Number Title Priority Date Filing Date
US690320A Expired - Lifetime US1992833A (en) 1932-09-03 1933-09-21 Two-way telephone and like electrical system

Country Status (5)

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US (1) US1992833A (en, 2012)
DE (1) DE623827C (en, 2012)
FR (1) FR761604A (en, 2012)
GB (2) GB408329A (en, 2012)
NL (1) NL37480C (en, 2012)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2511948A (en) * 1950-06-20 Hybrid circuit

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL80719C (en, 2012) * 1949-10-11
DE1062748B (de) * 1956-02-29 1959-08-06 Siemens Ag Einrichtung zur Vermeidung unerwuenschter Rueckkopplungen bei UEbertragungssystemen

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2511948A (en) * 1950-06-20 Hybrid circuit

Also Published As

Publication number Publication date
FR761604A (fr) 1934-03-23
GB408300A (en) 1934-04-03
GB408329A (en) 1934-04-03
NL37480C (en, 2012)
DE623827C (en, 2012)

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