1) CPD is defined as the value of the IC’s internal equivalent capacitance which is calculated from the operating current consumption without load. (Refer to Test . Integrated Circuit. Transistor Transistor Logic (TTL). 4−Line−to−16−Line Decoder /Demultiplexer. 24−Lead DIP Type Package. Description: The NTE is a. datasheet, circuit, data sheet: NSC – 4-Line to Line Decoders/Demultiplexers,alldatasheet, datasheet, Datasheet search site for.

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This encoder IC requires a voltage of 3V. The output code will remain the same as the previous detected code. This carried through to the input current requirements: It inhibits the detection of Hz.

The appliances to od controlled must be connected to telephone line through control unit. Press the respective code of the device whose status is to be checked. When you press a button in the telephone set keypad, a connection is made that generates a resultant signal of two tones at the same time.

For each positive going edge of the eatasheet pulse will trigger the flip flop. This is a control system through which you can control your appliances.

But these technologies have their own limitations. By using this system we can control the light from a control room or by the cell phone of the marketing person. This intern switches on the relay.


When either strobe input oof high, all outputs are high. The contents of the output latch are made available on the 4-bit output bus by raising the three state control input OE to logic high. Circuit Diagram of Local Control Section.

Device Control Using Telephone:

Uc signal goes to telephone exchange and the exchange sends a ringing signal to your set through phone line. By this transistor is forward biased and the output is obtained at the emitter of the transistor. Repeat the step ii. Here it does not require any such operator to operate this exchange. This feedback tone is datssheet only when the device is switched ON.

This is a control unit through which you can control your appliances.

National Semiconductor

This beep generator unit produces a short duration beep indicating than the device is already in switched ON state. The frequencies associated with various keys on the keypad are shown in figure A.

Here common anode seven segment display is used. When the detector recognizes the simultaneous presence of two valid tones known as signal conditionit raises the Early Steering flag ESt.

Now we follow the steps to test the proper switching of devices given below: However, due to the internal structure of theonly datasneet output can be enabled at a time.

It is active low output IC so when any output line is selected it is indicated by active low signal, rest of the output lines will remain active high. When the output of D flip-flop goes low the base voltage drops below 0. When a signal is sent from the remote telephone, the telephone interface circuit comes to receive the signal.


When you press the digit 5 in the keypad it generates a resultant tone signal which is made up of frequencies Hz and Hz. This circuit is useful to receive the telephone in the absence of the person. With an astable operation, the frequency and pulse width are produced by two external resistors and one capacitor connected between Vcc-Discharge RDischarge-Threshold Rand Threshold-Ground C. Until you press the key the feedback tone is heard. This IC datashheet of two D flip-flops.

Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you id read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. Where f a and f b are two different audio frequencies with A and B as their peak amplitudes and f as the resultant DTMF signal.

This period is calculated by the formula.

So theory will cover only the theory which explains the basic functionality of the working of a demultiplexor.