Back spacing apparatus

A back spacing apparatus includes a first means for providing speed information (E3, E4) corresponding to the speed of a tape, a drive source for rewinding the tape toward a supply reel (24) for back spacing, and a second means for providing an amount of electrical energy corresponding to the speed information (26) to the drive source (26) so that a length of the tape over which it is rewound toward the supply reel for back spacing is changed according to the transporting speed of the tape. The magnitude of the electrical energy is changed according to the speed information of the tape so that an amount of memory contents on that portion of a recorded tape rewound toward the supply reel for back spacing is made substantially independent of the transporting speed of the tape.

BACKGROUND OF THE INVENTION 
This invention relates to a back spacing apparatus for a tape player for 
use with a dictating transcriber machine, in which a tape is automatically 
rewound a predetermined amount for back spacing when the player is 
switched from a reproduce mode to a stop mode. 
When information recorded on a tape is transcribed, if there is a passage 
difficult to catch or follow, it is necessary to first stop the tape and 
then listen to it again by rewinding the tape to some extent and 
reproducing it. It is therefore necessary for the typist to effect the 
rewinding and playback operations of the tape each time any passage 
difficult to catch is encountered. Such a cumbersome operation is required 
in a case where typing, once interrupted for urgent business, is 
continued. 
In order to solve the above-mentioned inconvenience a back spacing 
apparatus for automatically rewinding a tape is currently used. For 
example, Japanese Patent publication No. 11211/77 or Japanese Patent 
Disclosure No. 71304/75 discloses a technique relating to such a back 
spacing apparatus. It is desirable that an amount of memory contents on 
that portion of a recorded tape rewound for back spacing be made 
substantially constant irrespective of the tape running or transporting 
speed at the time of playback. For a tape speed of either 2.4 cm/s or 1.2 
cm/s it is desirable that a length of a tape over which it is rewound for 
back spacing correspond to about one to two words (one to three seconds) 
of a normal conversation. In the conventional back spacing apparatus, 
however, no particular consideration is paid to the rewinding of the tape 
over a predetermined length with respect to a change in tape speed. That 
is, in the conventional back spacing apparatus the tape is rewound a fixed 
amount for back spacing irrespective of the tape transporting speed. For 
this reason, an amount of memory contents on that portion of a recorded 
tape rewound for back spacing varies dependent upon the speed at which the 
tape is recorded. Suppose, for example, that use is made of an apparatus 
adapted to rewind a recorded tape amount corresponding to a playback time 
of 2 seconds at a tape speed of 2.4 cm/s so as to present a corresponding 
amount of memory contents on the recorded tape. 
In this case, if a tape is recorded at a speed of 1.2 cm/s it follows that 
the recorded tape is rewound for back spacing so as to present those 
memory contents on the recorded tape which correspond to about 4 seconds. 
The longer the time during which said memory contents are reproduced, the 
lower the typing efficiency. In an apparatus adapted to rewind a recorded 
tape for back spacing so as to present an amount of memory contents on the 
recorded tape corresponding to 2 seconds at a tape speed of 1.2 cm/s, it 
follows that the tape is rewound an amount corresponding to only one 
second for back spacing, compared with the case where the tape speed is 
2.4 cm/s. In this case, the head or beginning of the backspaced word tends 
to be mutilated since a length of the tape over which the tape is so 
rewound is insufficient. 
SUMMARY OF THE INVENTION 
It is accordingly an object of this invention to provide a back spacing 
apparatus capable of automatically rewinding a recorded tape for back 
spacing so as to present a corresponding amount of memory contents thereon 
irrespective of tape transporting speed at the recording. 
In order to attain the above-mentioned object the back spacing apparatus of 
this invention includes a means for varying a length of a tape over which 
it is rewound, according to the transporting speed of the tape. Even if 
there is a variation in an amount of memory contents on a unit length of 
the tape, an amount of memory contents presented on the tape when it is 
automatically rewound for back spacing can be held in a predetermined 
range.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a capstan motor 10 is incorporated in a tape deck 
mechanism not shown and adapted to rotate a capstan of the deck at a 
predetermined rotation speed. Such a tape deck mechanism is disclosed in 
Japanese Patent Application No. 59487/79 filed on May 15, 1979 by the same 
assignee as that of this application. Japanese Patent Application No. 
59487/79 corresponds to U.S. Application Ser. No. 148,500, filed May 9, 
1980, assigned to the same Assignee as the present application. The motor 
10 is grounded at one end and connected at the other end to the emitter of 
an NPN transistor Q10. The collector of the transistor Q10 is connected to 
a power supply +Vcc through a switch S1 and the base of the transistor Q10 
is connected through a resistor R10 to the collector of the transistor 
Q10. The base of the transistor Q10 is also connected to the collector of 
an NPN transistor Q12 and the emitter of the transistor Q12 is connected 
to the emitter of an NPN transistor Q14. The emitters of the transistors 
Q12 and Q14 are grounded through a resistor R12. The collector of the 
transistor Q14 is connected to the collector of the transistor Q10. The 
transistors Q12 and Q14 constitute a comparator 12. 
A generator 14 is coupled with the motor 10 and has its one end grounded. 
An AC voltage signal is proportional to the rotation speed of the motor 10 
is generated at the other end of the generator 14. The signal e1 is 
supplied to one end of the capacitor C1 through an anode-to-cathode path 
of a diode D1. The other end of the capacitor C1 is grounded. That is, the 
signal e1 is rectified by the diode D1 and smoothed out 
(ripple-eliminated) by the capacitor C1. A DC voltage E1 proportional to 
the rotation speed of the motor 10 is developed at the cathode of the 
diode D1. The voltage E1 is divided at a voltage dividing point between 
resistors R14 and R16 into a voltage E2. The voltage E2 is applied to the 
base of the transistor Q12. 
A comparison or reference voltage E3 (or E4) is applied through a two-gang 
two-contact switch S2.sub.1 to the base of the transistor Q14. The 
comparator 12 compares a reference voltage E3 with the voltage E2. When 
E2&lt;E3, the collector current of the transistor Q12 is decreased and the 
emitter voltage of the transistor Q10 is increased, causing the rotation 
speed of the motor 10 to be increased to permit the voltage E2 to be 
increased. When, on the other hand, E2&gt;E3 the collector current of the 
transistor Q12 is increased and the emitter voltage of the transistor Q10 
is decreased, causing the rotation speed of the motor 10 to be decreased 
to permit the voltage E2 to be decreased. Eventually, the rotation speed 
of the motor 10 is controlled such that the voltages E2 and E3 become 
almost equal to each other. The motor 10 drives the capstan, not shown, 
for transporting the tape at a constant speed. For this reason, the 
rotation speed of the motor 10 is proportional to the transporting speed 
of the tape. In other words, the comparison voltage E3 (or E4) applied to 
the base of the transistor Q14 is converted to speed information 
corresponding to the transporting speed of the tape. 
The comparison voltage E3 is derived from a slider of a two-gang type 
variable resistor 18.sub.1 and supplied to the base of the transistor Q14 
through a first terminal of the switch S2.sub.1. The comparison voltage E4 
is derived from a slider of a two-gang type variable resistor 20.sub.1 and 
supplied through a second terminal of the switch S2.sub.1 to the base of 
the transistor Q14. The variable resistors 18.sub.1 and 20.sub.1 are 
grounded at their one end and connected at their other end to the cathode 
of a zener diode ZD1. The anode of the zener diode ZD1 is grounded and the 
cathode of the zener diode ZD1 is connected through a resistor R18 to the 
power supply +Vcc. The transistors Q10 to Q14, resistors R10 to R18, diode 
D1, capacitor C1, zener diode ZD1, variable resistors 18.sub.1 and 
20.sub.1 and switch S2.sub.1 constitute a motor control circuit 22 for 
controlling the rotation of the capstan motor 10. 
A reel motor 26 is coupled with a supply reel 24 of the tape deck. The 
motor 26 is also connectable to a take up reel not shown and adapted to be 
operated at the time of tape rewinding and fast forward. The motor 26 is 
coupled with the reel 24 during the rewind operation for back spacing. 
That is, the motor 26 provides a rewind drive source. The motor 26 has its 
one end grounded and its other end connected to the power supply +Vcc 
through a switch S3. The switch S3 is rendered ON at the time of normal 
rewinding and fast forward mode and OFF when a rewinding operation is 
effected for back spacing. The other end of the motor 26 is also connected 
to the emitter of an NPN transistor Q16. The collector of the transistor 
Q16 is connected to the power supply +Vcc and the base of the transistor 
Q16 is connected through a resistor R20 to a third pin of a timer IC 28. 
As the IC 28 use may be made of, for example, a MODEL NE 555 of Texas 
Instruments Inc. Ltd. A first pin of the IC 28 is grounded and fourth and 
eighth pins are connected to the power supply +Vcc. The fifth pin is 
grounded through a capacitor C2 and sixth and seventh pins are grounded 
through a capacitor C3. The sixth and seventh pins are connected 
respectively through variable resistors 18.sub.2 and 20.sub.2 to first and 
second terminals of a switch S2.sub.2. A contact terminal of the switch 
S2.sub.2 is connected to the power source +Vcc. The variable resistors 
18.sub.1 and 18.sub.2, and 20.sub.1 and 20.sub.2, are ganged or in 
interlock with each other and the switches S2.sub.1 and S2.sub.2 also in 
interlock with each other. 
The IC 28 and capacitors C2 and C3 constitute a monostable multivibrator 
30. The time constant of the multivibrator 30 can be changed according to 
the product of the capacitor C3 and variable resistor 18.sub.2 or 
20.sub.2. The multivibrator 30 is triggered when a negative trigger pulse 
e2 is supplied to the second pin of the IC 28, causing an output signal e3 
derived from the third pin of the IC 28 to become a high level. The high 
level of the signal e3 is sustained according to the time corresponding to 
the time constant (C3.times.18.sub.2 or C3.times.20.sub.2). The second pin 
of the IC 28 is connected to the power supply +Vcc through a resistor R22, 
and through a capacitor C4 to the collector of the transistor Q10. The 
resistor R22 and capacitor C4 constitute a differentiation circuit 32. 
Suppose that the switch S1 is rendered OFF with the tape deck switched from 
a reproduce made to a stop mode. Since in this case the collector voltage 
of the transistor Q10 is decreased to zero, negative trigger pulse e2 is 
applied to the second pin of the IC 28. As a result, the multivibrator 30 
is triggered and a high level signal e3 is supplied, during the time 
corresponding to the above-mentioned time constant, to the base circuit of 
the transistor Q16, causing a DC voltage signal E5 corresponding to the 
level of the signal e3 to be developed at the emitter of the transistor 
Q16. The reel 24 is rotated by the motor 26 and an automatic tape 
rewinding operation i.e. a back spacing operation is carried out. The 
rotation speed of the motor 26 during the back spacing operation is 
proportional to the voltage E5, and the back spacing operation time is 
proportional to the time during which the signal e3 sustains its high 
level. That is, the back spacing operation time is proportional to the 
time constant of the multivibrator 30. In other words, a length of the 
tape over which it is rewound toward the supply reel 24 is proportional to 
the time constant of the multivibrator 30. An electrical energy supplied 
to the motor 26 for rewinding is proportional to the product of the 
voltage E5 and the time constant of the multivibrator 30 or the period in 
which the motor 26 is powered. As mentioned above, the variable resistors 
18.sub.1 and 18.sub.2 or 20.sub.1 and 20.sub.2 are in interlock with each 
other and in consequence the time constant of the multivibrator 30 
corresponds to the comparison voltage E3 or E4 corresponding to the 
above-mentioned speed information. In order that an amount of memory 
contents on that portion of the recorded tape rewound a given distance for 
back spacing is made substantially independent of the transporting speed 
of the tape, the above-mentioned electrical energy is modified according 
to the above-mentioned speed information, as will be explained later. 
Suppose that the transporting speed of the tape is 1.2 cm/s with the 
switches S1 and S2 on the first contact side and that as shown in FIG. 2 
the back spacing time required for the tape to be rewound when the 
transporting speed of the tape is 1.2 cm/s is adjusted to, for example, 
500 ms. When in this case the slider of the variable resistor 18.sub.1 is 
moved so as to increase the tape speed to 1.2 cm/s+30%, the resistive 
value of the variable resistor 18.sub.2 is 30% increased, causing the time 
constant of the multivibrator 30 to be 30% increased to permit the back 
spacing time to be 30% lengthened. When, on the other hand, the tape 
transporting speed is reduced to 1.2 cm/s-30%, the back spacing time is 
30% shortened. If the tape transporting speed becomes 2.4 cm/s with the 
switches S1 and S2 on the second contact side, the same result is 
obtained. In this case, the time constant of the multivibrator 30 is set 
to two times as much as that when the tape transporting speed is 1.2 cm/s. 
As evident from the above-mentioned explanation, since the back spacing 
time can be extended in proportion to the tape transporting speed, an 
amount of memory contents on that portion of the recorded tape rewound 
automatically for back spacing can be made substantially constant 
irrespective of the tape transporting speed. 
Although this invention has been explained in connection with the 
embodiment in which the ratio between the tape transporting speed and the 
back spacing (rewinding) time is constant. On the other hand, as shown in 
FIG. 3, with the fixed time constant (C3.times.R19) of the multivibrator 
30 a voltage E6 proportional to the comparison voltage (E3 or E4) applied 
to the base of the transistor Q14 (FIG. 1) may be supplied to the motor 
26. That is, when the tape transporting speed is fast, for example, the 
comparison voltage E3 is high. At this time, the voltage E6 becomes higher 
and a voltage supplied to the motor 26 for back spacing becomes higher. 
Though in this case the time for the motor 26 to be conducted is constant, 
the rotation speed of the motor 26 is increased according to the increase 
of the voltage E5. That is, the voltage E6 can be varied by changing a 
voltage dividing ratio of a voltage dividing circuit (18.sub.2 +21) or a 
voltage dividing circuit (20.sub.2 +21). These voltage dividing ratios are 
varied according to the variable resistor 18.sub.2 or 20.sub.2. That is, 
when the tape transporting speed is faster, the tape rewinding speed 
becomes faster. It is therefore possible to maintain constant an amount of 
memory contents on that portion of the tape rewound for back spacing, 
irrespective of the tape transporting speed. 
This invention is not restricted to the embodiments as disclosed in the 
instant specification and drawings, and can be varied in a variety of ways 
without departing from the spirit and scope of this invention. For 
example, this invention can also be applied to a one-motor type tape deck 
in which a motor is used not only as a reel motor but also as a capstan 
motor. It is also possible to provide a pulse generator for generating a 
pulse corresponding to the rotation of the capstan flywheel as shown, for 
example, in U.S. Pat. No. 4,001,552, to detect the pulse width of an 
output pulse derived from the pulse generator and corresponding to the 
rotation speed of the capstan and to automatically vary the values of the 
ganged variable resistors 18.sub.1 and 18.sub.2 or 20.sub.1 and 20.sub.2. 
Or a voltage E5 applied to the motor 26 may be changed during the back 
spacing time according to the above-mentioned pulse width. As a motor 
control circuit 22 use may be made of a commercially available speed 
regulator IC, for example, a MODEL TCA 955 of Siemens Co., Ltd. (West 
Germany). Though various applications are disclosed in the Application 
Note of TCA 955, it is only necessary that the reference level (E3, E5) 
for servo control be changed according to the tape speed whatever 
application is used in this case.