US1655537A - Amplifier circuits - Google Patents

Description

Patented Jan. 10, 1928.

UNITED STATESn PATENT OFFICE.

JOHN W. FOLEY, QF IIBOGOTA, NEW JERSEY, ASSIGNOR T WESTERN ELECTRIC vCOMI- PANY, INCORPORATED, OIF NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

AMPLIFIER CIRCUITS.

.application led January 18, 1926. Serial No. 82,079.

This invention relates to telephone subsets, and has for an object to provide means energized from a central source for amplitying the received, or both the received and transmitted signals. Y

It is often desirable to equip a subscribers set for amplifying received or both the received and transmitted signals. `Electron discharge amplifiers are very suitable for this apparatus and it is desirable that the .devices be energized from a central source.

In accordance with a feature of this invention, a thermionic amplilier is provided for amplying the received energy at a subscribers set. Means are provided for supplying both the iilament heating current and the space current to this device from a central source. In addition, current is supplied to the transmitter from the same source;

In accordance with another feature of this invention, a thermionic ampliiier energized Jfrom a central source is provided for amplifying both the received and transmitted energies.

The invention will be morereadily understood by reference to the following description in connectionv with the drawing in which: Figs. 1, 2, 3 and 4 show telephone systems embodying subscribers sets arand Fig. 5 shows a system embodying a set arranged kfor amplifying both the received and transmitted slgnals. A

In Fig. 1 the subscribers sets A and B are connected by lines 6 and 7 to a central sta tion C which comprises the usual central stations equipment including a common battery 8 ,and repeating coil 9. At the subscribers station A the telephone transmitter 11 of the push-pull type is operative through a repeating co'il 12 to impress speech variations onto the line 6. An ainpliiier 13` is provided which is connected to the line 6 through the input transformer 14 and having a receiver 1 5 connected to its output terminals. central source 8, condensers 16 and 17 and retard coil 18 being provided for controlling the paths of the circuit and f signaling current in a manner described below. A switchhook 25 and a call bell 26 are'also provided. The switchhook 25 operates to deenergize the tube 13` by breaking the filament circuit ranged for amplifying the received signals;

The tube 13 is'energized from the when held in the down position by the weight of the receiver. The calling bell 26 is connected in series relation with the c0n,

denser 16 across line 6, the bell and condenser being so proportioned as to respond to curents of ringing frequencies sent over the lne.

Transformer 14 -.is of the usual step-up type for efficiently operating the tube 13.

-When the switchhook 25 is closed, direct current iiows from the positive terminal of `the battery 8 over line- 6 through the two sides of transmitter 11 in parallel, transformer 12, rheostat 27, retard coil 18, filament 28 of the vacuum tube 13, grid biasing resistance 29 and the primary of transformer 14 back over line 6 to the negative terminal of the battery 8. This current energizes the lilament 28 and makes the transmitter 11 operative. The-rheostat 27 isprovided jor the purpose of controlling the lilament current of the tubes. The grid of the tube 13 is maintained at a negative potential with respect to the filament by the drop inthe re- Y sistance 29.

The space current of the tube can be traced from the positive terminal of thebattery 8 through the calling bell 26, thereceiver 15 to the plate30 of the tube 13,- filament 28, resistance 29, primary7 winding of the trnsformer 14 and back over line 6 to the negative terminal of the battery. The inductive eiiect of the bell winding. 26prevents the flow of signalingcurrent through this circuit. Condensers 16 and 17 provide pathsfor the signaling current in the output circuit of the tube and the transmitter circuit respectively, while at the same time conning the direct current in the plate and filament to the proper paths. i

Subscriber set B is not shown in detail but may be similarly arranged or of any suitable type. Y

Fig. 2 shows a similar system except that in this subset circuit a single acting transmitter 32 is provided in place of the ushpull transmit-ter 11. The central station C is merely indicated, the battery and repeat ing coils not being shown in detail. lThe direct current flow in this circuit may be traced from the positive terminal of the central battery over the line 6 through switchhook 25,

transmitter button 32, filament 28, resistance 29, primary winding of the transformer 14, rheostat 27 over line 6 baclr to the negative terminal o-f the central battery. The space current circuit is the same as that for the system shown in Fig. 1.

` Fig'. 3 shows an anti-side tone subscribers set of the type shown in Fi of U. S. Patent 1,255,472 granted to A. Campbell, January 22, 1918. The element 33 is provided for balancing the line. It usually consists of a resistance and is incorporated in the transformer Winding. When the transmitter 32 is operated, it energizes both Windings 35 and 36 of the transformer 34, part of the energy being transmitted over the line 6 and the other part dissipated in the element 33. The current in these two windings being opposed, no energy is transmitted through the tube 13 to the receiver 15.

The filament heating circuit vfor this set :may be traced from the positive terminal of t-lie central battery over line 6 to switchhook where it divides, the main portion flowing through the transmitter 32 while the rest flows through resistance 33 and winding 36 to the retard coil 18, filament 28, resistance 29, connection 37, rheostat 27 back over the line v6 to the negative terminal of the central battery. The plate current can be traced from the positive terminal of the central battery over the line 6, through Winding of the calling bell 26, receiver 15, anode 30, filament 28, resistance 29, connection 37, rheostat 27, back over the line 6 to the negative terminal of theccntral battery.

The set in Fig. 4 is similar to that of Fig.

i 3 except that -the retard coil 18 is omitted,

` `and part of the talking current is permitted to flow through the filament. In this case, the filament heating circuit may be `traced from the positive terminal of the central battery over line 6, through switchhook 25,

transmitter 32 in parallel with resistance 33 and winding 36 in series, winding 35 of the primary winding of transformer 34, connection 38, filament 28, resistance 29, connection 37, rheostat 27 baclrover the line 6 to the negative terminal of 'thie central battery. The greater portion of the talking current flows through the low impedance path provided by the condenser 17 to Winding 35 while the remainder flows lthrough the parf allel path providedby-the filament 25 and resistance 29. In other respects, this set is the same as that shown in Fig. 3.v

Fig. 5 shows a set arranged for amplifying both transmitted and received energy. rlhe arrangement of this 'set is in general similar to that of the two-way one lelement type repeater circuit, the transmitter-receiver circuit 48 composed of the magnetic transmitter 39 and the receiver 15 connected in series to one lwinding of the transformer 40 being baltraced from the positive circuit of the central battery over line 6, upper contact switchhook 25, rheostat 27, retard coil 18, filament 28, resistance 29, connection 47 back over line 6 to the negative terminal of central battery. The space current circuit may be traced from the positive terminal of the central battery over line 6 through the windings of the bell 26, primary of transformer 42, anode 30 of impedance of the transmitter-receiver circuitv 48 as seen through the transformer 41, being balanced with that of the line 6, there is no difference of potential between the terminals of the primary winding of input transformer 44 and, therefore, no amplified energy is fed back into the tube 13 so as to cause singing.

This invention is not limited to the einbodinieiits shown which may be variousl modified without departing from the spirit of the invention as defined in the appended claims. t

What is claimed is:

1. In combination, an electron discharge device having input and output terminals, a space current circuit and a cathode heating circuit, a receiver connected to the output terminals of said device for receiving amplified signals therefrom, a source of direct current remote from said device, aline connecting said source and said device for supplying direct current and for transmitting signaling current to said device, means for connecting said discharge device to the line -to amplify the incoming signals transmitted f over said line, and connections for supplying anda transformer for connecting the line to the input terminals of the device and having such a ratio as to stepeup the voltage of the line.

4. A telephone system comprising a central station having a source of direct lcurrent, a line from said station for supplying direct current and for transmitting signaling current, a ,telephone substation, coinprising an electron discharge device having input and output terminals and a thermionic cathode, a receiver associated with the outputterminals of said device, a transmitter,

connections from said line for supplying drect current to said transmitter and said cathode in series, said Aconnections including an inducta'nce for preventing the ow of Signaling current therein, connections in para lel with a portion of said irst connections including the inductance and the cathode for transmitting signaling current from said transmitter to said line, said last connections including a condenser to prevent the flow of direct current therein, connections from said line for supplying spacecurrent to said device, sad connections including an inductance, and connections from said line to the input terminals of said device for supplying sivnalin current thereto.

5. telep one system according to claim 4 in which the substation includes a transformer for connecting the line with the input terminals of the electron discharge device, and an impedance associated with a portion of the primary Winding of said transformer for rendering said circuit antiside tone.

In witness whereof, I hereunto subscribe my name this 16th day of January, A. D.,

' JOHN W. FOLEY.

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