Patent GB-382794-A (GB)
Title: Call-answering device for telephone-station
IPC: H04M1/65
Filed: 1931-12-08
Abstract: 382,794. Sub - station equipment. BRAUN, R. M., 19, Ameisgasse, Vienna. Dec. 8, 1931, No. 34033. [Class 40 (iv).] A device for sending back an audible signal when a call has reached the wanted line comprises an oscillatory or vibratory member such as a pendulum. spring - controlled balance wheel, tuning fork, gong, &c. set in motion by an electromagnet energized by ring- ing current, the oscillation continuing after the cessation of ringing and causing impulses to be sent back along the line. The signal may indicate that the line is in order and, if the device is switched in by a party when he leaves his telephone, indicates his absence, two different signals being arranged to indicate long and short absence. In the form shown in Fig. 1, winding 3a of an electromagnet 3 bridged across the line by switch 4 is energized by ringing current and displaces pendulum or spring 1, and when ringing current ceases (e.g. during silent intervals) the pendulum is released and sends impulses over 6 to winding 3b, the resulting induced impulses in the line being heard by the calling party. In a modification, Fig. 2 (not shown), the pendulum swings between two contacts such as 6 and a switch is provided to include either or both contacts in circuit with winding 3b so that two different signals may be obtained, one twice the frequency of the other. In the modification shown in Fig. 3, magnet 23 energized by ringing current pulls up the spring 21 which releases a drop indicator 32 and connects condenser 29b, shunted by resistance 30, across the line. The core and armature 22 of the magnet are shaped to ensure magnetic action over a substantial distance. When the ringing current ceases, condenser 29b is sucsessively charged and discharged over contact 26 and resistance 30 to produce an audible signal at the calling station, but the flow of current is insufficient to operate the line relay of the called party. In a further modification, Fig. 4, an armature lever 42 controlled by a balance spring (watch spring) is moved from its position of equilibrium by a magnet 53 in series with winding 43a of magnet 43. When ringing current comes in magnet 43a releases the drop indicator 52 and magnet 53 moves armature 42 so that a spring 41 thereon engages contact 48. When ringing current ceases, spring 41. successively completes a charging circuit for condenser 49b over contact 46 and across the line, and a discharging circuit over winding 43b which induces an impulse in the line. Alternatively, by throwing switch 44b the condenser may be discharged over resistance 50b so that two different signals are obtainable. In another modification, Fig. 5 (not shown), particularly suitable for party lines, the magnet is polarized and its armature strikes a tuning fork which varies the flux of a permanent magnet through coils connected across the line and thereby sends a tone signal. In the case of party-line substations selectively rung by +ve or -ve current superposed on A.C. over one or other of the line wires, the electromagnet may be connected between the requisite wire and ground, a suitably poled rectifier being inserted in its circuit.