Programming instructions

FSK Source
 National Instruments Corporation 1-7 Multisim Component Reference Guide
1.10.3 FM Current Source
This component is the same as the FM voltage source, except that the output is measured in
current.
1.10.4 Characteristic Equation
The behavior of the FM current source is described by the same equation as in the FM Voltage
Source, with Vout replaced by Iout.
1.11 FSK Source
This source is used for keying a transmitter for telegraph or teletype communications by
shifting the carrier frequency over a range of a few hundred hertz. The frequency shift key
(FSK) modulated source generates the mark transmission frequency, f1, when a binary 1 is
sensed at the input, and the space transmission frequency, f2, when a 0 is sensed.
FSK is used in digital communications systems such as in low speed modems (for example, a
Bell 202 type modem - 1200 baud or less).
In this system, a digital high level is referred to as a MARK and is reproduced as a frequency
of 1200 Hz. A digital low level is referred to as a SPACE and is represented by a frequency of
2200 Hz.
In the example shown below, the frequency shift keying signal is a 5v (TTL) square wave.
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