Showing posts with label telephone. Show all posts
Showing posts with label telephone. Show all posts

Wednesday, June 5, 2013

Wire Telephone Ethernet Cable

Wiring Diagram  Cat5 Cable on General Manufacturing Instructions Pull The Cable Off The Reel To The
General Manufacturing Instructions Pull The Cable Off The Reel To The.


Wiring Diagram  Cat5 Cable on Ethernet Cable Wiring Diagram Straight Lg Gif
Ethernet Cable Wiring Diagram Straight Lg Gif.


Wiring Diagram  Cat5 Cable on Ethernet Cable To Work As Crossover Because Looking At These Diagrams
Ethernet Cable To Work As Crossover Because Looking At These Diagrams.


Wiring Diagram  Cat5 Cable on There Are Two Wiring Standards For These Cables Called T
There Are Two Wiring Standards For These Cables Called T.


Wiring Diagram  Cat5 Cable on How To  Wire An Ethernet And Phone Jack Using A Single Cat5e Cable
How To Wire An Ethernet And Phone Jack Using A Single Cat5e Cable.


Wiring Diagram  Cat5 Cable on Volvo C70 Wiring Diagram Cable Routing Harness Png
Volvo C70 Wiring Diagram Cable Routing Harness Png.


Wiring Diagram  Cat5 Cable on Ethernet Straight Thru Cable And An Ethernet Crossover Cable With A T
Ethernet Straight Thru Cable And An Ethernet Crossover Cable With A T.


Wiring Diagram  Cat5 Cable on Wire Telephone Ethernet Cable Jpg
Wire Telephone Ethernet Cable Jpg.


Wiring Diagram  Cat5 Cable on Cat 5 Ethernet Cable Standards Pin Out Assignments
Cat 5 Ethernet Cable Standards Pin Out Assignments.


Wiring Diagram  Cat5 Cable on Cables Page     How To Make Ethernet Cables  With Pictures
Cables Page How To Make Ethernet Cables With Pictures.


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Monday, May 13, 2013

Telephone transmitter

This is a simple, but very useful circuit that can be used to transmit telephone conversations. When the telephone receiver is on hook the voltage across the lines will be about 48 volts. The preset R7 is so adjusted to obtain a 24.7 V across between the cathode of D2 and ground. At this voltage the Zener diode D2 will be in breakdown and the transistor T1 will conduct. This makes the transistor T2 OFF. When the receiver is off hook, the line voltage drops to about 11 volts. This makes the transistor T1 OFF and subsequently the T2 ON. The T2 in switched ON condition will provide a DC path for the transistor T3 used in the FM transmitter section.
The transistor T3 is wired as a common emitter radio frequency oscillator. In simple words the transistor T2 serves as an ON/OFF switch for this oscillator. The modulated signal will be available at the collector of transistor T3 and the signal id fed to the antenna via capacitor C5.

Notes.

* Assemble the circuit on a good quality PCB.
* For L1 make 45 turns of 36 SWG enameled copper wire on the resistor R6 itself.
* The resistor R6 must be a 1M, 1 watt resistor.
* For L2 make 3 turns of 21 SWG enameled copper wire on a 12 mm plastic former.
* For antenna, use a 1 meter insulated copper wire.
* The capacitor C3 can be a 50pF trimmer.

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Monday, April 8, 2013

2 Line Intercom Cum Telephone Line Changeover Circuit

The circuit presented here can be used for connecting two telephones in parallel and also as a 2-line intercom. Usually a single telephone is connected to a telephone line. If another telephone is required at some distance, a parallel line is taken for connecting the other telephone. In this simple parallel line operation, the main problem is loss of privacy besides interference from the other phone. This problem is obviated in the circuit presented here. Under normal condition, two telephones (telephone 1 and 2) can be used as intercom while telephone 3 is connected to the lines from exchange. In changeover mode, exchange line is disconnected from telephone 3 and gets connected to telephone 2. For operation in intercom mode, one has to just lift the handset of phone 1 and then press switch S1.

As a result, buzzer PZ2 sounds. Simultaneously, the side tone is heard in the speaker of handset of phone 1. The person at phone 2 could then lift the handset and start conversation. Similar procedure is to be followed for initiation of the conversation from phone 2 using switch S2. In this mode of operation, a 3-pole, 2-way slide-switch S3 is to be used as shown in the figure. In the changeover mode of operation, switch S3 is used to changeover the telephone line for use by telephone 2. The switch is normally in the intercom mode and telephone 3 is connected to the exchange line. Before changing over the exchange line to telephone 2, the person at telephone 1 may inform the person at telephone 2 (in the intercom mode) that he is going to changeover the line for use by him (the person at telephone 2).

2-Line Intercom-Cum-Telephone Line Changeover Circuit DiagramAs soon as changeover switch S3 is flipped to the other position, 12V supply is cut off and telephones 1 and 3 do not get any voltage or ring via the ring-tone-sensing unit. Once switch S3 is flipped over for use of exchange line by the person at telephone 2, and the same (switch S3) is not flipped back to normal position after a telephone call is over, the next telephone call via exchange lines will go to telephone 2 only and the ringtone-sensing circuit will still work. This enables the person at phone 3 to know that a call has gone through. If the handset of telephone 3 is lifted, it is found to be dead. To make telephone 3 again active, switch S3 should be changed over to its normal position.
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