DE1000457B - Three-wire circuit for battery-free telephone systems - Google Patents

Description

GERMAN

Three-wire circuits for battery-less telephone systems are known. They have the advantage that the energy of a microphone resulting directly from the conversion of sound energy into electrical energy is won and is therefore low, is only forwarded to the telephone of the called subscriber, while in the two-wire circuit they also use the speaker's telephone and the microphone of the called flows in, so that the volume drops considerably. If there are more than two stations, the three-wire circuit is used however, it cannot be used without further ado, since the fixed assignment microphone-telephone in each case is only possible between two stations. It is already known that each station has one to be operated manually Assign a switch which, when operated, swaps the microphone and telephone connections will. This switch is z. B. each actuated at the calling station. The arrangement has the Disadvantage that the switch position has to be monitored by the operator, since the wrong position there is no speech connection.

It is also already known to assign a drop flap relay to each station, which reacts to the incoming inductor current responds, switches the speech device and after the end of the conversation by the hook switch is brought into the starting position. With this arrangement, the switchover takes place automatically, however, there is also the possibility of incorrect switching here. A called station is switched as a receiver until the hook switch has been lifted and put back on is. Is the call, e.g. B. by the absence of the participant, has not been noticed and calls this participant If another station later arrives, both stations are switched to receive, i.e. without communication. To avoid this incorrect switching, it is known that the drop flap by one of its own inductor to reset the excited magnet or mechanically through the axial displacement of the inductor, if the subscriber who has been called in vain wants to have a conversation and to do so activates his inductor. In any case, the switchover takes place electrically. A failure of the drop flap relay or one other transmission element leads to incorrect switching. Since batteryless stations are mainly used for important Telephone connections, which must be absolutely reliable, are such sources of error a great disadvantage.

According to the invention, a switch acting as a switching device for microphone and telephone when turning the call inductor is brought directly into its switching position and held locked by the hook switch in the switching position when the handset is removed until through on-three-wire dial device for battery-free
Telephone systems

Applicant: Telephony and signal construction

Lehner & Co. K. G., Essen-Kupferdreh,

Fahrberg 6

Dipl.-Ing. Wilhelm Schröder, Essen copper rotation,
has been named as the inventor

put the handset, the lock is released and the switching of the microphone and telephone is reversed is made. This activates the caller's micro-phone by actuating its own inductor switched over so that incorrect switching due to failure of electrical connection means cannot occur. According to a further embodiment of the invention, one controlled by the hook switch prevents Locking device to operate the crank inductor when the handset is on the hook. This is also Incorrect switching due to incorrect operation is ruled out as the switchover only takes place after lifting the receiver of the handset and actuation of the inductor takes place and is reversed by hanging up. An embodiment of the invention is shown in the drawing.

Fig. Ι shows a three-wire circuit according to the invention for four stations;

Fig. 2 shows an embodiment for the actuation of the switch.

In Fig. Ι ι the inductor of the subscriber station I is with the call selector 2, which is connected to the call lines 3, 4 and 5. The alarm clock 7 is on your own Call line 6. Microphone 9 and telephone 10 are with a pole, as well as inductor and alarm clock the common return line 8. The microphone and telephone are connected via the contacts of the hook switch 11 at the changeover switch 12, which can reverse the polarity of its connection to the speech lines 13 and 14.

Fig. 2 shows details of the switchover. The shaft of the inductor 1 is when the crank is operated pressed out in the direction of the arrow and puts the switch in the dashed position. Not by one The lock shown, however, the crank can only be operated when the handset 9, 10 from the hook switch is lifted, which is then through the

Effect of the spring 15 on the stop 16 applies. In In this position, the hook switch holds the switch 12 in the dashed position.

In Fig. Ι is thereby the microphone 9 with the line 14 and the telephone of station II, telephone 10 with line 13 and the microphone of Station II connected.

For the call, the call switch 2 was previously on line 5 and thus on the alarm clock of station II been laid. If station II picks up, its circuit remains unchanged, as shown. A faulty circuit is only possible if station II also operates its inductor, calls station I and station I has not yet hung up. However, this constructed case is of no practical importance. As a further indication there is still the possibility of the switch 12 being switched to be visible from the outside mark, e.g. B. by a mechanical indicator.

20th

Claims (2)

PATENT CLAIMS: I. Circuit arrangement for battery-free telephone line dialer systems with inductor call and with one of three conductors, all Intercom stations common speech line, each of which has a conductor for connecting the microphone and telephone as well as the third conductor for common return, and with to the Call stations provided switching devices for the microphone and telephone of the calling party Place, characterized in that a switching device for microphone and telephone Acting switch (12) when turning the call inductor (1) directly into its switching position brought and with the handset (9, 10) removed by the hook switch (13) in the switching position is kept locked until the lock is released by replacing the handset (9, 10) solved and the switching of microphone and telephone is reversed. 2. Circuit arrangement according to claim 1, characterized in that one of the hook switch controlled locking device prevents the operation of the crank inductor when the Handset (9, 10) is placed. Considered publications:
German patent specification No. 928 296. 1 sheet of drawings © € 09 740/149 12.56