Signal transducer

There is disclosed a signal transducer for extracting only the data components from information which has been modulated by different modulation systems. More concretely, the transducer provides two kinds of clock signals with respect to the information obtained by modulating the data under the frequency-modulation system or the modified frequency-modulation system, and extracts the data components from the information in accordance with one of the two kinds of clock signals.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a device for extracting only the data components 
from various kinds of information modulated by different modulating 
systems. 
2. Description of Prior Art 
There are various kinds of magnetic memory (or recording) devices such as, 
for example, magnetic tape, magnetic disc, magnetic drum, etc., which are 
used for electronic computers. These magnetic memory devices are better 
than punched tape in view of their reliability and high processing speed. 
As one example, when a magnetic head 2 is contacted with a magnetic disc 
(recording medium) 1 as shown in FIG. 1 of the accompanying drawing and 
the disc is rotated in the direction of an arrow 3, there is formed a 
track 1a, whereby recording and reproduction of information are effected 
on the track 1a. The information read out of the track 1a by the magnetic 
head 2 is subjected to frequency-modulation (FM) or modified 
frequency-modulation (MFM) to be described later. 
Signal waveforms concerning the frequency-modulation are shown in FIGS. 2A 
and 2B of the accompanying drawing, and signal waveforms concerning the 
modified frequency-modulation are shown in FIGS. 2C and 2D of the 
accompanying drawing. FIG. 2A shows the original signal, in which data 
consits of "1" and "0". FIG. 2B shows the frequency-modulated waveform of 
the original signal shown in FIG. 2A, in which the abovementioned data 
pulses are inserted between the adjacent clock pulses P.sub.C1, P.sub.C2, 
P.sub.C3, . . . . In other words, a pulse P.sub.D1 representing the data 
"1" is generated between the clock pulses P.sub.C1 and P.sub.C2, and a "no 
pulse" state representing the data "0" is generated between the clock 
pulses P.sub.C2 and P.sub.C3. 
In such a frequency-modulating system, since the data pulse is present 
between the adjacent clock pulses, the distinction between the clock pulse 
and the data pulse is clear. However the signal density is 
disadvantageously low. A modulating system that remedies this shortcoming 
of such a frequency-modulating system, is the modified 
frequency-modulating system. FIG. 2C of the accompanying drawing shows the 
original signal similar to that shown in FIG. 2A, in which the data 
consist of "1", "0", "0", "1". FIG. 2D shows the waveform of the original 
signal shown in FIG. 2C which has been subjected to the modified 
frequency-modulation. In this waveform diagram, a clock pulse P.sub.C is 
provided at the intermediate section of the adjacent data "0", "0" in 
place of the abovementioned clock pulse shown in FIG. 2B. In other words, 
the pulses P.sub.D1 and P.sub.D2 in FIG. 2D represent the data "1" shown 
in FIG. 2C, and a pulse P.sub.C1 represents the clock pulse provided at 
the intermediate portion of the two data "0", "0". Thus, according to the 
modified frequency-modulation system, the quantity of the information is 
twice as dense as in the abovementioned frequency-modulation system (which 
will be seen upon comparison of FIGS. 2D and 2B) despite the fact that the 
pulse number per unit time is less. However, even in the modified 
frequency-modulation system, there is a disadvantage in that, when 
rotational irregularity occurs in the disc shown in FIG. 1, the system 
tends to be more readily affected than the frequency-modulation system 
with the consequence that errors in reading the data can more easily 
occur. 
In view of the abovementioned advantages and disadvantages of the 
frequency-modulation system and the modified frequency-modulation system, 
both of them have so far been adopted equally in various kinds of 
computers depending on the type or model of such computers. Considering, 
however, the general use of the magnetic disc, it is desirable that either 
magnetic discs with information recorded under the frequency-modulation 
system or that recorded under the modified frequency-modulation system be 
used with the computer in common. 
SUMMARY OF THE INVENTION 
In view of the foregoing, it is the primary object of the present invention 
to provide a signal transducer capable of extracting data components from 
information recorded under different modulation systems. 
It is another object of the present invention to provide a signal 
transducer capable of using a magnetic recording medium with information 
recorded in the FM system and the MFM system. 
It is another object of the present invention to provide a signal 
transducer, capable of extracting data, having a simple construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The signal transducer of the present invention is so constructed that it 
may be adapted for use with the magnetic disc of the FM system and the MFM 
system, wherein the information obtained by modulation of data (either 
frequency-modulation and modified frequency-modulation) is introduced as 
input thereinto and this input information is transduced to the data 
signals alone. 
In the following, actual construction and operation of the signal 
transducer according to the present invention will be described with 
detail in reference to the accompanying drawing. 
FIG. 3 is a circuit construction diagram of the signal transducer according 
to the present invention, and FIGS. 4A to 4D show the waveforms of a 
signal flowing through the circuit in FIG. 3. 
In FIG. 3, signals which have been read out of a track 1a of a magentic 
disc 1 (recording medium) by a magnetic head 2 in FIG. 1 (information 
obtained by modulation of data) are introduced as input into a terminal 
4a. When the signal recorded in track 1a is obtained by the 
frequency-modulation, the data signal (information) waveform as shown in 
FIG. 4A is introduced as an input into the interminal 4a and when the 
signal is obtained by modified frequency-modulation, the data signal 
waveform shown in FIG. 4D is introduced. (The FM and MFM have already been 
explained in reference to FIGS. 2A to 2D.) The data signal input to 
terminal 4a is conducted to a phase synchronizing circuit 5 which is well 
known and may, for example, be a circuit incorporated in the floppy disc 
device FDD101A manufactured and sold by Hitachi Ltd., Japan, for example. 
The phase synchronizing circuit functions to control the phase of the data 
signal of FIG. 4A or 4D, to sent out, thereafter, a data signal which is 
substantially equal to the input to a computer 6 through a signal line 5a, 
and to send out a clock signal of FIG. 4B to a transducing circuit 7, as 
shown by a dash-line enclosure in the drawing, through another signal line 
5b. The transducing circuit 7 is constructed with a JK flipflop 8, AND 
circuits 9a, 9b, and an OR circuit 10. The clock signal shown in FIG. 4B 
is introduced as an input into the flipflop 8 and one of the inputs of the 
AND circuit 9b. An output from the flipflop 8 is introduced into one of 
the inputs of the AND circuit 9a. 
The input to a terminal 4b controls conversion of the above-mentioned clock 
signal, which opens the AND circuit 9a when an input signal "1" is 
introduced, and the AND circuit 9b when an input signal "0" is introduced. 
An output from the AND circuits 9a, 9b is introduced into the OR circuit 
10. An output from the OR circuit 10 is sent into the computer 6 to 
control the data signal transmitted thereinto through the signal line 5a. 
The computer 6 is one which is already known and may be, for example, LSI 
circuit HD1046503 manufactured and sold by Hitachi Ltd., Japan. The 
computer is capable of extracting the data components in the input 
information by changing the phase of the input clock signal. There, in 
case the input data signal from the signal line 5a is one which has been 
frequency-modulated (FIG. 4A), the output signal from the OR circuit 10 
should be able to make a distinction between the clock pulses P.sub.C1, 
P.sub.C2, P.sub.C3, . . . and the data pulses P.sub.D1, . . . in the 
signal of FIG. 4A. The waveform of the clock signal shown in FIG. 4B, 
which is output from the signal line 5b corresponds to the abovementioned 
clock pulses and data pulse (data component) at the low portion of the 
waveform, hence no distinction can be made between them. However, when the 
clock signal is frequency-divided in half and transduced into the waveform 
shown in FIG. 4C, the clock pulse can be distinguished since it 
corresponds to the high portion of the signal and the data pulse (data 
component) can be distinguished since it corresponds to the low portion of 
the signal. Accordingly, when the input data signal from the signal line 
5a is one which has been frequency-modulated, the signal "1" is applied to 
the terminal 4b, whereupon the AND circuit 9a opens and the input clock 
signal of FIG. 4B from the signal line 5b is frequency-divided in half by 
the flipflop 8 to be transduced into a waveform of FIG. 4C. The clock 
signal of FIG. 4C is then introduced as an input into the computer 6 
through the AND circuit 9a and the OR circuit 10. In the input data signal 
from the signal line 5a is one which has been subjected to modified 
frequency-modulation (FIG. 4D), the output signal from the OR circuit 10 
should be able to distinguish the clock pulses P.sub.C1, . . . from the 
data pulses (data component) P.sub.D1, P.sub.D2, . . . in the signal of 
FIG. 4D. In the waveform of FIG. 4B, the abovementioned clock pulse can be 
distinguished since it corresponds to the low portion of the signal, and 
since the data pulse corresponds to the high portion of the signal. 
Accordingly, when the input data signal from the signal line 5a is the 
modified frequency-modulated signal, the signal "O" is applied to the 
terminal 4b, whereupon the AND circuit 9b opens and the clock signal of 
FIG. 4B is introduced as an input into the computer 6 through the AND 
circuit 9b and the OR circuit 10. In this manner, the computer 6 is able 
to accept the clock pulse from the OR circuit 10 in accordance with the 
modulation system of the input data signal which has been subjected to 
frequency-modulation or modified frequency-modulation, and which is 
introduced through the signal line 5a, whereby the abovementioned data 
pulse (data component) from the data signal (i.e., information) can be 
extracted, and the computation result can be output at the terminal 4C. 
As described in the foregoing the signal transducer according to the 
present invention transduces the clock signal by selecting an input signal 
into the AND circuit, so that it can be adapted for use in either discs 
which have been subjected to the frequency-modulation or the modified 
frequency-modulation.