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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It uses same oscillator frequency used in the remote section so same crystal oscillator with frequency of 3. For each positive going edge of the clock pulse will trigger the flip flop. This circuit does not require any complex IC, so any one with little knowledge of ci can construct this circuit, because it does not need any programmable IC’s or programming.

The whole local control section except local telephone set is assembled in a single board, which is available in the market as common PCB. Above figure shows a single D-flip-flop. By pressing the number 5 in the key pad the output tone is produced which is the resultant of addition of two frequencies, at pin no.

Datasheet(PDF) – National Semiconductor (TI)

High speed signals were usually active low, for much the same reason. It has 10 pins. All inputs are buffered and input clamping diodes are provided to minimize transmission-line effects and thereby simplify system design. When either strobe input is high, all outputs are high.

National Semiconductor

The monostable multivibrater produces a single pulse when a triggering pulse is applied to its triggering input. It can also be controlled by PCO.

Each of the low and high frequency groups comprise four frequencies from the various keys present on the telephone keypad; two different frequencies, one from the high frequency group and another from the low frequency group are used to produce a DTMF signal to represent the pressed key.

This circuit consists of some passive components like resisters, capacitors. When you wish this section is to be work then you switch ON the DPDT switch otherwise your telephone is used for normal calling receiving purpose.


By varying the values of the R A and C A the ON period of the monostable multivibrater is changed according to the formula given above. Now power supply is connected and devices are also connected so that the whole section is ready for control device using a remote telephone set. The ring detector circuit is built around a monostable multivibrater constructed around timer IC This system is divided into two sections 1: This encoder IC requires a voltage of 3V. When a negative going pulse is applied to its triggering input at pin 2, the output of the IC goes high.

Auxiliary inputs provided blanking, lamp test and cascadable zero-suppression functions.

In such case if we have datzsheet which does not require any radiations or which fo not harmful, long remote control switch!! To perform any operations through remote phone line, the user needs to dial to the datashedt telephone to which the interfacing circuit is connected then the respective code of the device is dialed. When this key is pressed the output of the line decoder goes low. Provision is made for connection of a feedback resistor to the op-amp output GS for gain adjustment. For example, if the target application requires 16 7-segment LED displays, but your microcontroller only has 4 lines to select which display is active, this chip 74LS would provide a very effective method of essentially multiplying you selecting lines by a 4 times.

This signal is sent to the local control system through telephone line via exchange. This period is calculated by the formula.

The amplitudes of the two sine waves should be such that. The device selected from the Remote Section for control purpose, its code is displayed in this seven segment display.

The DTMF mode is shortly called as tone dialing mode. Check for availability of tone dialing mode in your telephone set. Taking a tour of the project: Local control section contains a telephone interface circuit, ring detector circuit, signal decoder circuit, device status check circuit, device controlling circuit, device status feedback circuit.


I understand how it works. I have a doubt in the demultiplexer section. While switching OFF the device this tone is not heard. This is same as lifting the receiver of telephone handset hook-off state.

Along with these DTMF generator in our telephone set provides a set of special purpose groups of tones, which is normally not used in our keypad.

National Semiconductor – datasheet pdf

Dstasheet IC is used as a multivibrater click here to download datasheet. The resultant frequency signal is called ” Dual Tone Multiple Frequency “. It is counterintuitive yes, but it is a well-established convention that the sort of devices that this part will be controlling will have active-low enable inputs.

In this type of PBEX only 12 extensions can be used. These flip-flops are used to latch the data that present at its input terminal click here to download datasheet.

A Typical frequency is shown in the figure below: Each or these 4-line-toline decoders utilizes TTL circuitry to decode four binary-coded inputs into one of sixteen mutually exclusive outputs when both the strobe inputs, G1 and G2, are low. This contains one telephone line and a control unit. These demultiplexer are ideally suited for implementing high-performance memory decoders.

Pressing digit 8 will produce the tone taken from tones Hz and Hz. However, due to the internal structure of theonly one output can be enabled at a time. Now make a call to your telephone set using a remote telephone set 74514 mobile phone. You can control devices from local telephone. This IC inverts the data on its input terminal and gives inverted output. These demultiplexers are ideally suited for implementing high-performance memory decoders.

When control signal is at high state, the outputs are nothing but the data present at its input terminals.