DE626396C - Circuit arrangement for coin operated telephones with microphone blocking - Google Patents

Description

GERMAN EMPIRE

ISSUED ON FEBRUARY 25, 1936

REICH PATENT OFFICE

PATENT LETTERING

CLASS 21a ³ GROUP 8O2O

Patented in the German Empire on February 12, 1933

The present invention relates to a circuit arrangement for coin operated telephones, in which the microphone is kept locked until the called subscriber reports, so that the speaking guest can hear the subscriber who answers, but not with him yet can speak.

With such payphones, however, fraud is usually possible in that the Speech communication with the called party is established in that the Intercom guest speaks into the telephone and thereby an, if imperfect, so at least Sufficient understanding achieved. For

avoidance of this drawback, damping circuits have already been developed in which a low-resistance resistor is placed in parallel with the telephone and microphone, and furthermore Another high-resistance inductor or resistor is connected to the microphone circuit is. Through a cashier contact, which is activated in a known manner by pressing a button is transferred with simultaneous cashing of the inserted amount, the high-resistance Resistance short-circuited and the low-resistance one in the shunt to the telephone Resistor switched off; This known damping circuit does not form a perfect one Blocking of the flow of the microphone and communication by speaking inadequately prevented from entering the telephone.

The present invention now provides a complete blockage of the microphone flow and so much attenuation of the alternating speech currents generated by the telephone achieved that an understanding with the called subscriber by speaking into the Telephone is practically excluded. According to the invention this is achieved in that into the speech loop that can be bridged by an operating measure by the speech guest Capacitor of small capacity is connected, * through which the incoming, through discussion Speech currents generated by a microphone are less attenuated than those caused by talking to the telephone Streams of speech in an outgoing direction. Those generated by speaking into the microphone Speech streams, however, have higher frequencies than those resulting from talking on a telephone conventional design generated speech currents, and the speech currents of higher frequencies are attenuated less strongly than speech currents by a capacitor with a small capacity lower frequency.

In the drawing, an embodiment of the circuit according to the invention is shown. The reference symbols have the following meanings.

*) The patent seeker stated as the inventor:

Frits Appelius in Berlin-Spandau.

M is the microphone, I is an induction coil. The remote receiver is labeled F. _{The capacitor C 1} , which has a capacity of about 0.01 MF, is connected into the speech loop. The capacitor C ₁ can be short-circuited by the auxiliary contact K , which is only closed when the speaking guest pushes the cashier button to put the amount in the coin collecting container

ίο can get. Contact K is a double break contact. If the speaking guest wants to establish a connection in the outgoing direction, the contact K is first opened by inserting the coin, so that the short circuit for the pulse contact nsi is canceled and dialing pulses can go out unhindered. When the called subscriber answers, speech communication with the same is not possible because the microphone current is blocked _{by the capacitor C 1.} The speaking guest can hear the called subscriber, since the capacitor C ₁ offers no significant resistance for the incoming speech currents. By pressing the cashier button, the contact if is returned to the initial position, so that the capacitor C ₁ is short-circuited again. Immediate readiness to talk is available for incoming calls.

It is irrelevant here whether the auxiliary contact K is returned to the rest position directly by the cashier key itself or by other switching means that are dependent on the actuation of the cashier key. The auxiliary contact K could also remain in the actuated position until it is hooked in, and instead another switching means dependent on the cashier (e.g. relay) exercise the same effect as the resetting of the auxiliary contact.

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Claims (1)

Claim: Circuit arrangement for coin operated telephones with microphone blocking by a Auxiliary contact, characterized in that in the speech loop an operating measure of the speaking guest (pressing the number button) bridgeable capacitor of small capacity (about 0.01 MF) switched is by which the incoming speech streams generated by talking to a microphone are less attenuated become more outgoing than the streams of speech evoked by talking on the telephone Direction. 1 sheet of drawings