Patent GB-190405308-A (GB)
Title: Improvements in and relating to Electric Contact Devices such as Resonance Relays for Telephone Systems.
Inventor: PEDERSEN PEDER OLUF
Filed: 1904-03-03
Granted: 1905-01-12
Abstract: 5308. Pedersen, P. O. March 3. Telephone systems; relays.-Relates to resonance relays of the type described in Specification No. 16,810, of 1901, and to a telephone relay system in which they are applied. The relays are arranged so that the electrical connection obtained is good and lasting. In one arrangement, the vibrating string is suspended between binding-posts over an electromagnet through which is passed a variable or alternating current of the same frequency as the vibrations of the string. A small armature is arranged in the centre of the string over the magnet. As the effect of the magnet is cumulative, it causes the string to vibrate until the armature is carried sufficiently near to the' magnet to be drawn into contact therewith and retained, thereby closing a circuit through the string and the core of the magnet. With currents of different frequency the string is not affected by the magnet. If the string is made of iron or steel, the armature may be dispensed with. In a modification, the poles of a horse-shoe electromagnet are bent close together, so that the string, or an insulated contact carried thereby, connects them. In the arrangement shown in Fig. 5, the string a operates resilient contacts m, n, which are independent of the attracting-maguet. In a modification, in which the contacts m, n are superposed, the string engages the lower one and separates them. In another modification, the contact is carried by the string out of engagement with the upper one, and into engagement with a contact arranged below it. The magnet which operates the string can be used as a retaining-magnet. In the arrangement shown in Figs. 8 and 11, the string t is weighted at x and suspended by a binding-screw u over insulating- prisms v, w. It is loaded by a small weight y. It is attracted by the in-turned pole-pieces 1 of an electromagnet z. The core and pole-pieces 3 of a retaining-electromagnet 2 are arranged in circuit with, and fastened to, a metal plate 4. When the vibration of the string reaches a certain amplitude, it is retained by the magnet 2 so as to close a contact between the string and one or both polepieces 3. The string may consist of a brass wire carrying a light armature. Fig. 12 shows, diagrammatically, an arrangement for making it possible for a whole set of telephone subscribers to use the same double line to the central, without a conversation being overhead or interrupted. Each subscriber can also ascertain whether the line is free or occupied. Two similar telephone apparatus A, B are provided in the example shown. Two strings 7, 8, of different frequency and operated respectively by magnets 15, 16 and connected to one line-wire 5, can by their vibration close circuits containing batteries 9, 10 respectively. A contact 12 operated by an electromagnet 11 can close a circuit from a battery 14 through the magnets 15, 16. Two double relays 17, 18 and 19, 20 are provided. The device operates as follows:-The subscriber A is called from the central by sending an alternating or variable current, of frequency corresponding to the string 7, through the linewire 5. This current passes from the wire 5 through the strings 7, 8, wire 46, electromagnet 11, wires 47, 48, contact 29, wire 49, contact 50, and wire 51 to the other line-wire 6. The string 7 vibrates, until caught by the magnet 15, which has been energized by the magnet 11. The battery 9 now sends a current through the wires 52, 53, electromagnet 17, wire 54, line 5, string 7, and the core of the magnet 15. The magnet 17 now attracts its armature, so as to raise a lever arm 21 having a hooked end, and release a lever 25. This lever is drawn to the left by a spring so as to open contacts 26, 29, and close a contact 27. The current from the central now passes partly through the line 5, strings 7, 8, wire 46, magnet 11, wires 47, 55. 56, a contact 13 operated by the magnet 11, wire 57, and line 6, and partly through the line 5, wires 54, 58, the usual fork lever, contact 40, wire 59, contact 43, wires 60, 61 short-circuiting the usual inductor 34, wire 62, bell 35, wires 63, 64 and 65, contact 27, wires 66, and main 6. When the telephone is lifted from the fork, all is in order for speaking, the primary circuit being closed through a microphone battery 33, wires 67, 68, contact 69, wire 70, microphone 32, wire 71, primary coil 36 of the transformer, and wire 72. The secondary speaking circuit is closed through the wires 5, 54, 58, fork lever, contact 41, wire 73, secondary coil 37, wire 74, telephone wires 75, 64, 65, contact 27, and wires 66, 6. The lever 21 being raised, contacts 23, 24 operated by it are closed, and a contact 22 is opened, so that a battery 30 can energize the magnet 20, which opens a, contact 83 and blocks the apparatus B. At the calling off, the central is closed to earth through a battery which, cooperating with the battery 30, sends a current from the line 6, via the battery 30 and magnet 18, to earth at 31. The magnet 18 returns both relays to rest. To call the central, a button 42, having two active positions, is pushed in to close a contact 44 and interrupt a contact 43. The microphone battery 33 then sends a current through the magnet 17 and bell 35 if the contact 28 is closed, but, if the line is in use, this contact is open, and the bell will not ring. The pushbutton may be secured in an intermediate position so as to ring as soon as the line is free. This battery is too weak to cause the armature of the magnet 17 to be attracted until the button 42 is pushed right in, so as to short-circuit the bell. If the central has called a subscriber, it cannot call another, till the relays have been returned to the position of rest. The central can, however, call two subscribers simultaneously by sending out currents corresponding to one string, before ceasing to send out currents corresponding to the other string. If A wishes to speak to B, the central is closed to earth, and then both A and B are rung up together.