Patent GB-190404176-A (GB)
Title: Improvements in and relating to Multiplex Telegraphy.
Inventor: FIELD STEPHEN DUDLEY
Filed: 1904-02-19
Granted: 1905-02-02
Abstract: 4176. Field, S. D. Feb. 19. Telegraphs.-Relates to quadruplex apparatus in which one transmission is effected by current reversals and the other by variations of current strength, and to the superposition, thereon of vibratory currents of different frequencies, thus enabling transmission to be effected in multiplex. Figs. 2 and 3 show the transmitting-apparatus for quadruplex working. The transmitting-key No. 1 for current reversals controls an electromagnet 3 adapted to actuate a rocking bar 1 normally held by a spring 4 in the position shown. The transmitting-key No. 2 for variations of current strength controls an electromagnet 14, which, when energized, rocks the lever 6 and lifts the frame 8 which carries the contact plates 13. These plates tend to rise equally under the pressure of a spring 11. The frame 8 is connected to line, and the four generators d', d<11>, d<111>, d<1111>, the voltages of which are indicated in the Figure, are connected to earth on the one side, and to contact pins 5<1>, 5<11>, 5<111>, 5<1111> on the other. In the position shown in Fig. 2, the key No. 2 is closed and the key No. 1 open. The voltage supplied to the line is - 300. If the key No 2 is open, the frame 8 is depressed, and the contact plates 13 are inclined upwards towards the ball-joint 12, the pin 5<11> then making contact with the plate 13, and the line voltage being reduced to -100. If the key No. 1 is depressed, the bar 1 rocks over, and the voltage becomes +100 or +300 according as the key No. 2 is open or closed. Consequently, every depression of the key No. 1 produces a current reversal, and every depression of the key No. 2 a change in strength. Moreover, all changes of voltage take place by steps of 200 volts at a time, three steps being made in reversing from - 300 to +300 volts, owing to the successive contacts of the pins 5<11>, 5<111>, 5<1111>. The resistances 15<1> are of 200 ohms each. The receiving-apparatus for the two transmissions just described is a relay which, as shown in Fig. 14, comprises two coreless coils differentially or otherwise wound, and capable of vibrating separately within or around a common magnetic field and of operating a lever adapted to engage with two contacts. The construction of this relay forms no part of the invention. The apparatus used for the superposed harmonic transmissions is shown in Fig. 4. The reed 16 is kept in vibration by the electromagnet 17 and the make-and-break contact device 19. Two electromagnets 22, 23, suspended as shown in Fig. 5, are normally attached to the reed, giving it a relatively low frequency. Lf either of the keys 20, 21 is depressed, the corresponding electromagnet 22 or 23 is released from the reed, and the frequency increased accordingly. If both keys are depressed, the frequency is a maximum, and it is arranged that this frequency shall affect both of the receiving-instruments, which respond independently to the two lower frequencies. The circuit of the transmitting-battery 30 is closed alternately through the coils 35, 36 of a divided coil C by the successive contacts made by the reed at 32, 33, induced currents being sent to line. A subsidiary induction coil 34 is inserted between the reed contacts and the coil C, and a condenser c bridges the wires from the reed contacts. To prevent shock in picking up an electromagnet 22 or 23 which his been disengaged, the circuit of the electromagnet may be closed through the reed itself. The receiving-apparatus for the harmonic transmissions is shown in Fig. 11. The reeds 42, 43 are differently tuned, but both respond to the maximum frequency of the transmitting-reed 16, as stated above. The reeds are polarized by a bar magnet 45. The reeds close local circuits containing sounders 48, 49. Wires or links 50, connected to the reeds and tensioned centrally by rubber bands 51, give smoothness of movement to the reeds. In a modified form of the apparatus shown in Fig. 4, the coils 34, 35, 36 are on the same laminated core, which has an air-gap with a variable iron shunt. In the form shown in Fig. 8, the coils 34 are on separate cores so that the mutual inductance can be varied by angular movements of the shuttleshaped "armature." Other re-arrangements of the coils 34, 35, 36 and of the condensers are described.