DE2432452C2 - Circuit arrangement for generating loop criteria of a defined length - Google Patents

Description

In telephone systems with multi-frequency dialing (DTMF) it is primarily used to carry out reversing functions a special key (the so-called flash key) providing a defined short-term interruption used (see DE-PS 21 55 916). It is also known to press a button on a subscriber set assign two different meanings, depending on whether during the Pressing the button the handset is lifted or not. That way, for example, came through the actuation of the earth button depending on the position of the hook switch both a query but a direct call can also be initiated (see the literature on »Telephone PBX with ESK «, Siemens and halske AG. Order number 1 -32 40-002).

The short-term interruption of the loop current, which can be achieved by pressing the flash button, can, for example cause the connection of a dialing receiver with the handset unhooked, such as this, for example is necessary to initiate the inquiry.

The invention is based on a combination of features as set out in the preamble of the main claim . The object of the invention is to create additional signaling that differs from the known short-term interruption in such a circuit arrangement with simple means, with which a Another feature that differs from the callback can be initiated by the subscriber when the handset is on-hook.

This object is achieved by the combination of features specified in the characterizing part of the main claim. An essential principle of Invention thus consists in the predetermined position of the handset when the handset is in place Hook switch sends a fixed-time current surge from the subscriber set to the switching system and to generate this current surge also in the subscriber set

ίο to use the existing flash button anyway.

In a further development of the invention, a combination of features resulting from claim 2 can then result recommend, if the period of contact is anyway with predominantly mechanical means

is causes wind, so that only to illustrate the invention minor mechanical additions are still necessary.

However, if the temporal dimension of the contact and possibly also the contact itself is realized with predominantly electronic means, one of the combinations of features evident from claims 3 to 5 can be recommended in a further development of the invention.
The structure and mode of operation can best be illustrated in conjunction with two by the drawings F i g. 1 and 2 recognize occupied exemplary embodiments.
F i g. 1 shows a purely mechanical and
F i g. 2 a mechanical-electronic solution, each time including the familiar flash button.

In both examples, the central device indicated by the control means C , the hook switch U, the call path W connected when the hook switch is in the rest position and the speaking and dialing device /! Which forms the connection of the line a / b are similar.

Only the switching center connected to the flash key F is different. In FIG. 1, this is an additional working contact incorporated into the flash control or, in the simplest case, a single-spring working side that can be specified by the switch position F = 2.

The one with the handset picked up, so

Switching position LJ = 2 is known; it leads to a defined short interruption when the Flash button F is pressed. What is new, however, is the clearly manageable process with the handset in place, ie the hook switch position U = 1, which can be clearly evaluated in fast systems.

The recognized signal can have the meaning of »direct call«.

Fig. 2 shows in principle the same as Fig. 1. The only difference is the formation of the current closure, which is advantageously achieved here while maintaining the mechanical structure, ie without changing the addition of the known flash key F, only by adding an electronic switch. This switching additive essentially consists of a transistor 7Ί, a high-ohmic resistor R and a diode D. To improve the switching properties, the arrangement, as shown here, can be expanded by a cascading transistor addition T2.

■ "■ In the idle case, which is the switch position U = 1, according to the handset on the phone, a current that is far below the functional limit for the central device flows through the resistor R and the diode D , which, however, if the flash key F the short circuit to the control path of the transistors

Order is canceled, enables the full switching of the arrangement. The diode D is superfluous for this process on sieve, its meaning only occurs when the handset is lifted, i.e. the fork switch position U = I. The purpose then to be fulfilled is to block the control circuit that otherwise runs through the actuated hook switch.

1 sheet of drawings

Claims (5)

Patent claims: 1. Circuit arrangement for the delivery of loop criteria of a defined length in telephones provided for carrying out the multi-frequency dialing (DTMF) with the aid of the flash button which produces a short-term interruption of the subscriber loop during the working position of the hook switch regardless of the duration of the flash button, characterized in that the Pressing the flash button (F) while the hook switch (U 1) is in the idle position causes the short-term closure of the subscriber loop as an additional signal. 2. Circuit arrangement according to claim 1, characterized in that the short-term closure of the subscriber loop is provided by a switching element (FT) coupled to the flash key mechanism (79) (FIG. 1). 3. Circuit arrangement according to claim 1, characterized in that the short-term closure of the participant loop (a. B) is provided by an electronic contactor (Ti, TT) controlled by the flash button (/}. 4. Circuit arrangement according to claim 3, characterized in that the electronic contactor is formed by a transistor circuit (Tl, TT) which can be activated with the opening of the flash contact (Fi). 5. Circuit arrangement according to claim 4, characterized in that the formation of a control current for db transistor switching path (T \, TT) is blocked by a diode when the hook switch (UT) is actuated (F i g. T).