Desire was burning the circuits of her mind as well.
This increase may be made evident by making the loop of wire one arm of a Wheatstone's bridge and so arranging the circuits that the oscillations pass through the fine wire.
At the death of Wesley the figures were: 313 preachers, 119 circuits and mission stations, and members.
[[[Construction Of Circuits]] This form of insulator is still largely used and is a very serviceable pattern, though possessing the defect that the porcelain cup is not removable from the iron bolt on which it is mounted.
For the longest circuit to be worked, the shorter circuits being brought up approximately to a level, as regards resistance, by the insertion of resistance coils in the circuit of the transmitting apparatus of each shorter line.
If long circuits were worked direct with ordinary instruments, high battery power would be required in order to send sufficient Single current to actuate the apparatus.
Repeaters (or translators, as they are sometimes termed) are in Great Britain only used on fast-speed circuits; they are in no case found necessary on circuits worked by hand, or at " key speed " as it is called.
One of the longest circuits upon which it has been successfully worked is that between St Petersburg and Omsk, a distance of approximately 2400 miles of iron wire, with three repeating stations.
The heavier cores, with the consequent advance in speed of working attainable, have necessitated the introduction of automatic sending, the instruments adopted being in general a modification of the Wheatstone transmitter adapted to the form of cable signals, while the regularity of transmission thus secured has caused its introduction even on circuits where the speed cannot exceed that of the ordinary operator's hand signalling.
In 1885 Preece and Heaviside proved by experiments made at Newcastle that if two completely insulated circuits of square form, each side being 440 yds., were placed a quarter of a mile apart, telephonic speech was conveyed from one to the other by induction, and signals could be perceived even when they were separated by 1000 yds.
Telephonic speech between these two circuits was found possible and good, the communication between the circuits taking place partly by induction, and no doubt partly by conduction.
By stretching on the island and mainland parallel wire circuits earthed at each end, good telephonic communication over an average distance of 62 m.
A system by which the primary and secondary circuits were " turned " or syntonized by including condensers in the circuits.
He proved that when so syntonized the circuits are inductively respondent to each other with a much less power expenditure in the primary circuit than without the syntony.
Thus, in the case of one station and one moving railway carriage, there is a circuit consisting partly of the earth, partly of the ordinary telegraph wires at the side of the track, and partly of the circuits of the telephone receiver at one place and the secondary of the induction coil at the other, two air gaps existing in this circuit.
Marconi 2 imparted practical utility to this idea by tuning the two circuits together, and the arrangement now employed is as follows: - A suitable condenser C, or battery of Leyden jars, has one coating connected to one spark ball and the other through a coil of one turn with the other spark ball of a discharger S.
These two circuits are so adjusted that the closed oscillation circuit, consisting of the condenser, primary coil 1 See German Patent of F.
Fleming devised an arrangement in which a multiple transformation takes place, two oscillation circuits being interlinked inductively, and the last one acting inductively on the open or antenna circuit.
If L and N are the inductances of any two circuits which have a coefficient of mutual inductance M, then M/-/ (LN) is called the coefficient of coupling of the circuits and is generally expressed as a percentage.
Two circuits are said to be closely coupled when this coefficient is near unity and to be loosely coupled if it is very small.
It can be shown that if two circuits, both having capacity (C) and inductance (L), are coupled together inductively, then, when oscillations are set up in one circuit, oscillations of two periods are excited in the other differing in frequency from each other and from the natural frequency of the circuit.
This receiver therefore, like the transmitter, consists of an open and a closed electric oscillation circuit inductively connected together; also the two circuits of the receiver must be syntonized or tuned both to each other and to those of the transmitter.'
These inter-area or long-distance lines, called trunk circuits in England, terminate at one exchange in each local area, and between that exchange and the various district exchanges junction circuits are provided for the purpose of connecting subscribers to the trunk lines.
The single-wire earthed circuits used in the early days of telephony were subject to serious disturbances from the induction caused by currents in neighbouring telegraph and electric light wires, and from the varying potential of the earth due to natural or artificial causes.
Variation in resistance of the transmitter spoken into causes a variation of the pressure at the line terminals of the impedance coils, and since those terminals are common to the two circuits the variable E.M.F.
An improvement in this respect has been effected by the insertion of condensers in the cord circuits, coupled with the use of two sets of impedance coils, one set on each.
The impedance coils shown connected between the battery and the lines and between the latter and the transmitters are joined up non-inductively as regards the transmitter circuits, but inductively as regards the secondary circuits.
At the outgoing end the circuits are multipled on the subscribers' switchboard, while at the incoming end they terminate in plugs on a special incoming junction switchboard upon which the subscribers' lines are multipled in the usual way.
In America, on farmers' circuits, ten or more stations are frequently connected to one line; but in England ten is practically the maximum.
Circuits to the trunk exchanges where the necessary connexions are made between the trunk line and the junctions.
The call is controlled by the trunk operators, the junction circuits being equipped in such a manner that the subscribers' signals appear at the trunk exchanges, from which point disconnecting signals are sent automatically to the local exchanges, when the connexions between the trunk and the junction circuits are removed.
During the five years1819-1824there had been made from Hull 17 circuits with a membership of 7600, and Hull itself had 3700 more.
Soon after came the gradual process by which the circuits handed over their mission-work to a central Connexional Committee.
Particulars of calls are now passed between trunk centres to a great extent over telegraph circuits superposed upon the trunk lines.
The idea of automatic telephony is to substitute for the operator of the manual exchange an electromechanical or other switching system, which, controlled in its movement by the action of the subscriber, will automatically select, connect and disconnect circuits as desired.
Junction circuits are usually made up of 20 or 40 lb conductors.
Another method of distribution, largely adopted, is to run the lead cables into the interior of blocks of buildings, and to terminate them there in iron boxes from which the circuits are distributed to the surrounding buildings by means of rubber-covered wires run along the walls.
In circuits possessing high resistance and capacity and low inductance per mile, telephonic currents are rapidly attenuated, and the higher the frequency the more rapid is the attenuation.
Many circuits have been " loaded " in the manner proposed by Pupin during recent years, especially in underground cables, and it has been found in practice that the transmission value of these when loaded is approximately from three to four times their value unloaded.
The introduction of inductance coils into such circuits renders them more susceptible to trouble from atmospheric electricity and more sensitive to leakage variations.
The number of trunk wire centres open on the 31st of March 1907 was 533, and the total number of trunk circuits was 2043, containing about 73,000 m.
There are now four circuits between London and Paris, one between London and Lille, and two between Londofi and Brussels, the last carrying an increasing amount of traffic. Experiments have been made in telephonic communication between London and Rome by way of Paris.