Examines the issue of re-making an explosive device phones means at hand to work on the lock.
It just so happened that the domestic telephone service has chosen the way of saving on their own users. And, despite the increased cost of long distance telephone calls, the introduction of per-minute charges for local calls, inventing different additional tariffs on Fax machines and caller ID the quality of communication we have with You has not improved. And many (especially people living in big cities) phone connected by paired scheme or how it is called through the lock. In the future, it is them that will be discussed.
So, first consider the principle of a conventional line without lock. To the subscriber fit line which is in the "standby" mode is supported voltage 60V at a current of about 40 mA. When calling the voltage ranges from 60V to 120V c has a frequency of about 25 Hz. Because of this and the pendulum oscillates in mechanical calls to regular phones. This system is already of old age, but nobody is going to change, and in this sense is not. Everything was fine, but to save (in this case twice) on the number of wires, domestic telephony commissioned blockers, which affected the disastrous inconvenience users of the system. These devices have proliferated. Unlike conventional line is that the users also suitable line from the PBX, but two for one. The polarity of the supply voltage which varies with a certain frequency, and when using the phone, or the call remains in the polarity that will correspond to that user. To ensure the selectivity of the challenge and to exclude the possibility of eavesdropping, subscribers are connected according to the following scheme:
The scheme of the calling device Panasonic phones
The voltage ringing when the phone is connected by paired scheme is lowered, and it is not enough to enable the chip. You can fix this if you reduce the resistance of the resistor R1 3.3 K and the capacitance of the capacitor C2 to 4.7 µf. This revision is used by me for a long time. While none of the customers complained. Qualitative characteristics phones it does not deteriorate.
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