DE1115774B - Circuit arrangement for controlled selection and / or free selection of a step switch for telecommunication, in particular telephone systems - Google Patents

Description

The invention relates to selector switches with push ratchet drives (hereinafter referred to as "step switches" called), as used as rotary dials or rotary dials in self-connecting telephone and telecommunications systems come into use.

As is well known, a step selector is composed of an electromagnetically operated push latch, which move the voter arms one step at each excitation (or de-excitation) of an electromagnet of the voter advances. In addition to the controlled election also a free choice of the voter enable what is necessary for alternating excitation and de-excitation of the indexing magnet the stepping mechanism is provided with interrupter contacts, which are in the excitation circuit for the winding and are opened when the coil is energized, thereby closing the excitation or incremental circuit interrupt. The subsequent de-excitation of the coil causes the breaker contacts to close again with subsequent re-activation of the magnet. The breaker contacts have the Disadvantage that they require a very careful adjustment and cause malfunctions as a result of wear give or at least require a considerable amount of maintenance.

The circuit arrangement according to the invention for controlled selection and / or free selection of a step selector with an electromagnet with two windings for telecommunications, in particular telephone systems is characterized in that instead of interrupter contacts of the stepping mechanism a transistor is provided and connected in such a way that the excitation or stepping winding of the electromagnet lies in the collector-emitter circuit, while the one with this winding is magnetic coupled feedback winding is arranged in the base circuit of the transistor, and that the incremental pulses or continuous potentials for controlling the voter are fed to the base.

The invention will now be explained in more detail with reference to the drawing, which shows it as an example illustrating a rotary selector with a control circuit that enables the voter is either controlled by means of impulses or advanced automatically (free choice).

The drawing shows a step-by-step switch mechanism RS known per se with two contact banks A1, A 2 and the contact arms w 1 and w 2 associated therewith, which are advanced by means of an indexing and pawl arrangement (not shown) under the control of an electromagnet DM. It is assumed that for the onward circuit arrangement

for controlled voting and / or free voting

a step selector for telecommunication,

in particular telephone systems

Applicant:

Associated Electrical Industries Limited,
London

Representative: Dipl.-Ing. E. Schubert, patent attorney,
Siegen, Oranienstr. 14th

Claimed priority:
Great Britain of February 26, 1959 (No. 6751/59)

Bloomfield James Warman, London,
has been named as the inventor

switch the contact arms wl and w2 by one switching step, the electromagnet DM must first be energized and then de-energized. The electromagnet DM has two magnetically coupled windings C1 and C 2, of which Cl is the exciter or step-up winding, and C 2 is the feedback winding. The excitation winding Cl is in the collector-emitter circuit of a transistor T, while the feedback winding C 2 is switched into the base circuit of the transistor between the base electrode and a voltage source for positive bias potential (+). The magnetic coupling between windings Cl and C 2 brings about regenerative feedback from the emitter-collector control circuit to its base circuit; however, the positive bias on the base electrode normally prevents oscillation control by preventing the transistor from conducting. A negative incremental pulse Vp, which is transmitted to the base electrode of the transistor T by means of a capacitance coupling network C, R , and a polarized one

109 710/131

Rectifiers Rf have the consequence that the transistor becomes conductive. The resulting current flow in the winding Cl causes a control process by the feedback pulses C 2. The current flow through the transistor therefore increases rapidly, and the magnetic flux that is induced by the excitation winding Cl and passes through the feedback winding C 2 in a concatenation increases until saturation. After saturation is reached, the regenerative effect ceases and the transistor is switched off, ie not conducting, until the magnetic flux has decayed. Since the excitation winding C1 has been excited and then de-excited again, the stepping mechanism RS has been advanced by one switching step. The selector can thus be operated in a controlled manner by means of the incremental pulses Vp.

If instead of an incremental pulse Vp a continuous negative direct current potential is applied to the transistor base electrode via a wire, then a control effect similar to that described above is achieved, which, however, is continuously repeated, whereby a free selection process is achieved that lasts until the negative The preload on core 1 disappears. The fact that this negative potential is transmitted by a test or home run or reset segment of the step-by-step switch mechanism enables you to switch freely or to run into the zero position in an easily visible manner. For example, in the drawing, the wire 1 is shown so as to contact the bank Al of the stepping mechanism RS is connected via a resistor R1 and rise to the contact arm contacts Rt Wl, said contact bank is used as the test bench.

The return or reset step h of the contact bank Al is connected to negative potential via the normally closed or break contact sh, while the other steps 1 .. 0 of the contact bank each in selective manner via changeover ml ... m 0 to either negative or Earth can be switched on. When contact st closes, the negative potential applied to contact h of contact bank A1 triggers the free selection process of the type described above, this switching process lasting as long as contact arm tv 2 has a negative potential at steps 1, 1, 3 via the switch ml, ml, m3 ... The free selection process comes to an end at that bank contact, for example contact 5, which has been applied to earth potential instead of the negative potential by actuating the associated switch m S. A subsequent home run can be achieved by means of a similar control effect, which is triggered by the fact that the contact m 5 is turned over and the contact sh is opened. These switching measures for the free selection can be provided either instead of or in addition to the switching measures for the controlled selection.

Since the transistor can have a considerable gain, the stepping mechanism can be actuated by a low-power current source which can be switched electronically, instead of mechanically or electromechanically, for example by means of transistor binary pairs. In addition, in the case of pulse-controlled incremental switching, the incremental switching effect can be achieved by a brief pulse P , as can be supplied by an electronic or a ferrite core gate control circuit. The incremental control circuit is therefore particularly suitable for electronic control. It should also be noted that the circuit for the actuation signal, e.g. B. the incremental pulse P or the negative bias on the wire 1, neither the excitation winding Cl nor the feedback winding C 2 includes. Since this circuit is not inductive, it can, if necessary, be of great length and run in a cable without causing interference (crosstalk); in addition, for the removal of the preload needs for the free choice of. a test bench of the stepping mechanism, for example A1, the contact arm wl of this contact bench must not be designed as a bridging contact arm, but it is sufficient if it only has contact with one contact at a time during the contact transition.

Claims (4)

PATENT CLAIMS: 1. Circuit arrangement for controlled selection and / or free selection of a step selector with an electromagnet with two windings for telecommunications, in particular telephone systems, characterized in that a transistor (T) is provided in place of interrupter contacts of the stepping mechanism and is switched such that the exciter - Or stepping winding (Cl) of the electromagnet (DM) lies in the collector-emitter circuit, while the feedback winding (C 2) magnetically coupled to this winding is arranged in the base circuit of the transistor, and that the stepping pulses or continuous potentials to control the selector of the Base are fed. 2. Circuit arrangement according to claim 1, characterized in that the incremental pulses the conductivity of the transistor (T) changed and a resulting oscillator effect is triggered on each incremental pulse. 3. Circuit arrangement according to claim 1 and 2, characterized in that for the free selection process a continuous potential is switched on, which in the electromagnet (DM) a The oscillator effect triggers, each time the stepping mechanism advances, and that switching means (ml-mO) interrupt the aforementioned potential, when the step switch reaches a predetermined position. 4. Circuit arrangement according to claim 3, characterized in that the switching means for interrupting the continuous potential has a test contact bank (A 2) with a switching arm (W 2) via which the aforementioned potential of the transistor base electrode is supplied until the switching arm reaches a contact (ml-mO) which is marked by the absence of the aforementioned potential. 1 sheet of drawings © 109 710/131 10.61