DE3002392C2 - Circuit arrangement for feeding in a special dial tone for telephone connections switched to the telephone order service - Google Patents

Description

The invention relates to a circuit arrangement for feeding in a special dial tone for the Telephone order service switched telephone connections, with the normal dial tone through a Additional modulation is changed in order to alert the subscriber to an existing switchover do.

An important feature of the service to the telephone subscriber is the telephone order service (Fe-AD). On request, a subscriber line can be connected to the Fe-AD so that during the Absence of the subscriber for him, incoming calls received and Messages can be left. For this purpose, the subscriber is provided with an Fe-AD subscriber circuit (Fe-AD-TS) assigned, which causes the calls in parallel to the existing switchover can reach an Fe-AD inquiry station. While the existing switchover, the subscriber can make outgoing calls unhindered and also Accept calls if he answers before entering the Fe-AD answering station.

So that a participant is made aware of the existing switchover to the Fe-AD when he uses his telephone set for an outgoing call is in modern switching equipment provided to send a special dial tone to this subscriber in the switchover state. This measure is known and published, for example, in the 1971 electrical telecommunications logbook on page 55.

To enable this, it is necessary for switching systems to be equipped with this feature: that the dial tone at the relevant feed point is in the correct form - i.e. at existing switchover - is switched on. For this purpose, especially with centrally controlled Switching systems corresponding commands, as well as programs and services, for example in the

ίο Elective rates, this advance payments required for decentralized, to install switching systems that are controlled in a state-of-the-art manner, would be particularly expensive and would lead to considerable increases in price. This is especially true of that Subsequent additions and the necessary changes to existing system parts.

It is therefore the object of the invention to provide a circuit arrangement that only works at the points must be attached where the special dial tone is required,

and does not require changes to existing circuitry at any point

The solution to this problem takes place in that the assigned to a switchable subscriber Connection circuit switching means are arranged, which upon detection of an AND link from the Criteria: existing switchover and subscriber wants connection, close a switch that has a Tonfrequsnzspannung with a different from the dial tone Frequency can reach the speech arteries

An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. If a subscriber TIn is to be switched to the telephone order service, a special subscriber circuit Fe-AD-TS is connected to this connection. It is then possible to activate the switchover at any time. For this purpose, the latching relay U is made to respond via a control line E 2. If a call is made for the subscriber TIn in this state, the switching sequence relay t / F is triggered by the ringing current via the speech wire a coming from the line selector LW. With the contact u / 3, the caller is started for the telephone order service Fe-AD-AS. This voter adjusts to the called connection. The call signal can then reach one of the telephone answering stations. The connection intended for the switched subscriber can be received and answered by the officer. After termination of the connection, and also if the switched subscriber reports before the order service officer enters, the relay UF is switched off in a manner not shown.

Since the subscriber is connected to the speech wires via the idle pages of the contacts uf \ and uf2 despite the existing switchover, he can make outgoing calls. When he picks up his handset, he receives the normal dial tone from the switching system via the voice lines. Since there is now a switchover, a potential deviating from the idle state is fed to the switching means SM via the line / 1. The potential on subscriber line a reaches input / 2 and indicates that the subscriber has picked up his handset. The two lines / 1 and / 2 are combined in an AND operation, and an output signal A appears when the subscriber sets up an outgoing connection in the switched state. With this signal, the amplifier V

permeable, and the audio frequency coming from the generator C reaches the primary winding of the transformer L. From there it is transmitted through a transformer to the speech wires and thus added to the normal dial tone.

At the beginning of the dialing of the subscriber, the dial tone is switched off from the switching system in a known manner. This is done by the change in potential that can be seen on line / 2 when the loop current is interrupted as a result of the dialing pulse. The previously mentioned UN D link is then no longer fulfilled and the switchable amplifier V is blocked. This state is retained by a storing switching means even if the loop current begins to flow continuously again after the end of a series of elections or after the end of the elections, and the AND link would actually be fulfilled again.

If the connection is released by the subscriber, a long-lasting one is recognized when it is recognized Loop current interruption on line / 2 for it ensured that all switching means are in their resting state. Triggering a connection can also be determined by the fact that a higher negative potential appears on the line / 2 than when it is closed Loop is the case After the idle state has been set, the switching means are again ready for a new connection to perform the same function as previously described.

1 sheet of drawings

Claims (4)

Patent claims: 1. Circuit arrangement for feeding a special dial tone for telephone connections switched to the telephone order service, the normal dial tone being changed by an additional modulation in order to draw the subscriber's attention to an existing switchover, characterized in that switching means (SM) are assigned to a subscriber that can be switched over. are arranged, which when recognizing a LJN D link from the criteria: existing switchover and subscriber wants connection, close a switch (V) , which allows a tone frequency voltage with a frequency deviating from the dial tone to the speech wires 2. Circuit arrangement according to claim 1, characterized in that the link is fulfilled when there is a voltage characterizing the existing switching on a control wire (E2) and a voltage characterizing the flow of loop current is recognized on the subscriber line. 3. Circuit arrangement according to claim 1, characterized in that the switch (V) consists of a lockable amplifier. 4. Circuit arrangement according to claims 1 to 3, characterized in that when the loop current is interrupted, for. B. when delivering dial pulses, the switch (V) is blocked, and that this state is maintained by storing switching means even when the loop current flows continuously again.