: : : A L S - Advanced Electronic Systems : : :

ALS-CT-05	ALS-CT-06
ALS-CT-07	ALS-CT-08
ALS-CT-09	ALS-CT-10
ALS-CT-11	ALS-CT-12
ALS-CT-13	ALS-CT-14
ALS-CT-15	ALS-CT-16
ALS-CT-17	ALS-CT-18
ALS-CT-19

8 CHANNEL TIME DIVISION MULTIPLEXING AND DEMULTIPLEXING TRAINER

This kit facilitates the students in learning Pulse Amplitude modulation and de modulation, multiplexing of the sampled signal and reconstruction of the original signal.

FEATURES:
	8 Channel multiplexing and demultiplexing.
	On board variable Sine Triangle and square wave generators.
	Low Pass Filters.
	Various test points to observe the process at various stages.
	Potentiometers to vary the frequency of the signal sources.

TECHNICAL SPECIFICATIONS:
	Input Channels: 8 numbers8
	Switching: Time Division Multiplexing
	Modulation: Pulse Amplitude Modulation
	On board Signals: Sine - 1no, Triangle - 1 no, Square - 2 no.s
	On-board Signal frequency Range: 50 Hz to 500Hz adjustable @2V pk-pk
	Sampling clock: 64 K Hz
	Test Points: 26 nos.
	Interconnections: 2mm Sockets with patch cords.
	Power: External 5V,+12V and -12V

LIST OF EXPERIMENTS:
	To Study 8 channel Multiplexing and Demultiplexing.
	To Study address generation and its use in multiplexing and demultiplexing.
	To Study Pulse Amplitude Modulation and demodulation.

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This trainer provides an opportunity to study carrier modulation of digital signals.
There are various carrier modulation techniques required for transmission of digital information. Amplitude Shift Keying (ASK) is one such modulation scheme. Digital
signal is represented by a sequence of '0's and '1's. In ASK a carrier frequency is
switched On if the data bit is '1' and switched off if the data bit is '0'. This trainer
provides a bit pattern generator and carrier signal required to carryout the
experiment.

This trainer provides an opportunity to study carrier modulation of digital signals.
There are various carrier modulation techniques required for transmission of digital
information. Phase Shift Keying (PSK) is one such modulation scheme. Digital signal is
represented by a sequence of '0's and '1's. In PSK. Carrier signal which is in-phase or
180 degrees out of phase is switched depending on whether the Input Data is '1' or '0'.
This trainer provides a bit pattern generator and carriers with 0 deg. and 180 deg.
Phase difference.

This trainer provides a facility to study carrier modulation of digital signals. There are
various carrier modulation techniques required for transmission of digital
information. Frequency Shift Keying (FSK) is one such modulation scheme. Digital
signal is represented by a sequence of '0's and '1's. In FSK a carrier signal is switched
between two frequencies depending on whether the Data bit is '1' or '0'. This trainer
provides a bit pattern and carrier generator.

Pulse Position Modulation (PPM) is a basic Pulse Modulation technique. The trainer
provides complete set up to the students for performing experiments to learn PPM.
They can study Sampling, Pulse Modulation, and Demodulation & Signal
reconstruction process. Separate circuits are provided for each stage.

This trainer provides an opportunity to study CODEC. A CODEC has two parts, Encoder
and Decoder. Encoder converts the input audio signal sampled at regular intervals into
PCM data. Decoder converts the input PCM data to an equivalent analog voltage. While
doing this it applies either A-law or Mu-law. It also provides anti-aliasing filter.
The trainer uses HD44233P CODEC which is an A-law codec.

Pulse Amplitude Modulation (PAM) is a basic Pulse Modulation technique. The trainer
provides complete set up to the students for performing experiments to learn PAM.
They can study Sampling, Pulse Modulation, and Demodulation & Signal
reconstruction process. Separate circuits are provided for each stage.

Pulse Width Modulation (PWM) is a basic Pulse Modulation technique. The trainer
provides complete set up to the students for performing experiments to learn PWM.
They can study Sampling, Pulse Modulation, and Demodulation & Signal
reconstruction process. Separate circuits are provided for each stage.

Frequency modulation (FM) conveys information over a carrier wave by varying its
frequency. In analog applications, the instantaneous frequency of the carrier is directly
proportional to the instantaneous value of the input signal. A simple form of FM often
used for digital communications is FSK. Digital Data can be sent by shifting the carrier's
frequency among a set of discrete values, a technique known as Frequency Shift Keying
(FSK). In FSK frequency changes abruptly in contrast to FM.

Amplitude modulation (AM) conveys information over a carrier wave by varying its
amplitude. In analog applications, the instantaneous amplitude of the carrier is directly proportional to the instantaneous value of the input signal. A simple form of AM often used for digital communications is ON-OFF keying, a type of Amplitude Shift Keying (ASK) by which binary data is represented as the presence or absence of a carrier wave.

This trainer provides an opportunity to study carrier modulation of digital signals.
There are various carrier modulation techniques required for transmission of digital
information. Differential Phase Shift Keying (DPSK) is one such modulation scheme. It
is similar to PSK. In PSK before keying, DATA is not conditioned. In DPSK the Input DATA
is conditioned to NRZM format before keying. After demodulation, the DATA is
reconditioned to get back the original DATA
This trainer provides a bit pattern generator and carriers with 0 deg. and 180 deg.
Phase difference.

This trainer provides an opportunity to study PCM. In order to send analog signals over
a digital communication system, we need to convert analog signals to digital ones. The
process is performed by analog-to-digital-converter (ADC). The analog signal is
sampled (i.e. measured at regularly spaced instants) and then quantized (i.e.
converted to discrete numeric values. The converse actions to ADC converting digital
signal to its analog equivalent) is performed by digital-to-analog-converter (DAC)
Sampling is done by a sample/hold (S/H) amplifier that stores the analog value on a
capacitor at the instant of measurement. It provides a quantizing resolution of 1 in 256
using 8-bit ADC. Each analog sample is matched to the nearest binary level.

This trainer provides an opportunity to study analog signal sampling and to prove the
Sampling theorem.
In this trainer the sine wave signal available on the trainer is sampled at regular
intervals to produce amplitude modulated signal. The sampling frequency can be
selected from 4 different sampling rates. It is also possible to change the duty cycle of
the sampling clock from 0% to 100% using DIP switches. It is possible to select
between Flat sampling type of output or Natural sampling type of output using a
jumper. Finally in the demodulator it is possible to choose either a single two pole filter
or two no.s of two pole filters connected in cascade.

In order to send messages to far off places, it is important to use any of the modulation
techniques. In the case of Amplitude and Frequency modulation techniques, the
modulated signal is in the analogue form. This analogue signal, while being transmitted, is subject to various kinds of distortions. In communication systems, such distortions in the transmission path can be avoided by coding the information signal and then transmitting it as pulse patterns of 0 and 1, or in other words digitizing it. Delta modulation is one such technique. In this the analog signal is sampled regularly at fixed intervals and the previous sample is compared with the present sample. If the present sample is more in amplitude compared to the previous sample it is coded as 1 otherwise, 0. Since it carries only the difference information rather than the full information unlike PCM, it utilizes a very small bandwidth. This trainer is built on the concept of linear delta modulation. It is called linear because the local decoder producing the feedback signal is a linear network.