Parallel and continuous playback circuit for an audio cassette deck of the double-deck type

A parallel and continuous playback circuit for an audio cassette deck of the double-deck type (A-deck and B-deck) includes signal detectors for detecting the tape signal of the playback head of each deck during playback, pulse generators for generating arbitrary pulses when an unrecorded blank portion is detected by the signal detectors, a deck selector for selecting the playback mode of the A-deck or the B-deck in parallel, i.e. alternately, upon detection of an unrecorded portion on the tape being played back in the other deck and for pausing playback of the tape in the deck in which the unrecorded portion is detected, and an error prevention circuit for preventing erroneous operation of the deck selector after selection of the other deck and upon encountering and unrecorded portion such as as the start of the tape in the selected deck. The playback circuit offers the advantage of playing back of the tape cassette in the other deck when an unrecorded portion is detected on the tape cassette in the deck currently being played back, thus alternating playback between the A-deck and B-deck in distinction to double cassette decks of the serial play or relay play type which play back the entire cassette in one deck before changing playback to the cassette in the other deck, and so on. The parallel and continuous playback circuit thus alleviates the tedium of listening to unrecorded blank portions of the cassettes by switching playback to the other deck of the double-deck.

BACKGROUND OF THE INVENTION 
The present invention relates to a parallel-continuous playback circuit for 
audio cassette decks of the double-deck type, particularly to a circuit 
which can pause the A-deck for a moment if a blank (unrecorded) part is 
detected on playing back a tape in the A-deck, and play back a tape in the 
B-deck at the same time, so that the tapes in the A-deck and B-deck can be 
played back in parallel. 
In the past, a conventional cassette deck of the double-deck type first 
completed the playback of the tape in the A-deck, and next played back the 
tape in the B-deck (e.g., serial or relay playback). 
Thus, for example, when a conversation tape is inserted in the A-deck and a 
music tape is inserted in the B-deck, and the power supply is turned on, 
then the conversation tape is continuously played back, thereby causing 
the user tedium. 
SUMMARY OF THE INVENTION 
The present invention has for its object to provide a parallel playback 
circuit for an audio cassette deck of the double-deck type in which, if an 
unrecorded part is detected on playing the tape in a cassette in the 
A-deck, a tape in the B-deck is automatically played, and if an unrecorded 
part between the recorded portions of the tape in the B-deck is again 
detected, then the playback is again changed to the A-deck. 
According to the present invention, there is provided a parallel and 
continuous playback circuit for an audio cassette deck of the double-deck 
type comprising: a control means for causing pulse generators to produce 
an arbitrary pulse when a recorded portion of a tape is played back and 
detected in the A and B-decks, a selection means for selecting the play 
mode or the stop mode of the A-deck and the B-deck by logical processing 
of the generated pulse signals of the control means, and a parallel 
playback means for preventing incorrect operation of the selection means 
in order to play the tapes in a cassette deck of the double-deck type in 
parallel.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will be now described in more detail with reference 
to the accompanying drawings. 
As shown in FIG. 3, the present invention is composed of the signal 
detectors 30 and 35 to detect the unrecorded part between the recordings 
on a tape by detecting the tape signal of the tape playback in the audio 
head, the pulse generators 40 and 45 to produce an arbitrary pulse when an 
unrecorded part is detected by signal detectors 30 and 35, the deck 
selector 10 to select the A and B-decks in parallel in response to the 
output pulses of the pulse generators 40 and 45, and the error-prevention 
parts 20 and 25 to prevent incorrect operation of the parallel control 
between the unrecorded parts in playback-mode. 
As shown in FIG. 2, when the recording 1 is reproduced in the playback mode 
of the A-deck, when an unrecorded part is detected, then the A-deck goes 
to the pause mode and the playback mode is transferred from the A-deck to 
the B-deck, playing back the recording 5 of the tape in the B-deck. 
When an unrecorded part is next detected in the B-deck, the playback mode 
is transferred to the A-deck, and the B-deck enters the pause-mode, and 
then the recording 2 in the A-deck is played back. 
To explain the operation of the present invention in detail, first, turning 
the power supply on, the outputs Q and Qof the J/K flip-flop in the deck 
selector 10 become HIGH and LOW-level, respectively,.so that the A-deck 
enters the playback mode, but the B-deck enters the pause mode. 
When the tape in the A-deck is played in the playback mode, the signal 
detector DET 1 of the signal detection part 30 provides a HIGH-level 
output, and it is inverted through the OR gate OR1 and inverter IN1, and 
the inverted signal is applied to the pulse generation part 40. 
On the other hand, the signal detector DET 2 of the B-deck in the 
pause-mode provides a LOW-level output to the OR gate OR3 and another 
input of the OR gate OR3 is connected to the supply voltage Vcc through 
the transistor Q3 of the error prevention part 25, so the output of the OR 
gate OR3 becomes HIGH-level, then the signal applied to the pulse 
generation part 45 through the inverter IN2 is LOW-level. 
Thus, because of the LOW-level signal outputs of both pulse generation 
parts 40 and 45, in the same initial state, a LOW signal from OR gate OR2 
is applied to the clock terminal CK of the J/K flip-flop so that the 
A-deck is maintained in the playback mode, and the B-deck in the pause 
mode. 
If an unrecorded blank tape part is scanned on playing the tape in the 
A-deck in playback mode, then the signal detector DET 1 of the signal 
detection part 30 provides a LOW-level signal and a HIGH-level signal is 
applied to the pulse generation part 40 through the inverter IN1. 
As the pulse generation part 40 provides a HIGH-level output signal, the 
output of gate OR2 goes to HIGH-level, thereby providing an edge signal of 
a rising pulse to the clock terminal CK of the J/K flip-flop, then the 
outputs Q and Qof the J/K flip-flop become LOW and HIGH-level, 
respectively, so that the A-deck is changed to the pause-mode, while the 
B-deck is changed to the playback mode. 
On the other hand, the HIGH signal of the output terminal Qof the J/K 
flip-flop is applied to the error-prevention part 25, then the transistor 
Q3 is turned on during the time capacitor C3 is being charged to the 
HIGH-level. 
And, the supply voltage Vcc is provided to a terminal of the OR gate OR3 so 
that the pulse generation part 45 does not provide a HIGH-level signal 
even if the B-deck starts to playback an unrecorded part between the 
recordings on the B-deck tape and the output of the signal detector DET 2 
is LOW-level. 
That is, when the A-deck is changed to the PAUSE-mode upon detecting an 
unrecorded part on playing back the tape in the A-deck, and the B-deck 
goes to the playback mode, the PAUSE phenomenon of the B-deck occurring 
due to no detection of the tape signal at the tape's start point or an 
unrecorded part of the tape can be prevented as mentioned before. 
Therefore, from the time that the capacitor C3 is fully charged, that is, 
when the transistor Q3 turns off, the B-deck begins to play the recording 
regardless of the lack of the B-deck tape signal. 
And, if an unrecorded blank part between the recorded portions is again 
detected on the B-deck tape, then the output of DET 2 becomes LOW-level, 
and the transistor Q3 is already turned off, so that the output of the OR 
gate OR3 becomes LOW-level. 
The output of the OR gate OR3, being LOW-level, is inverted by the inverter 
IN2 and is provided to the pulse generation part 45, and the pulse output 
through the transistor Q4 is applied to the OR gate OR2 of the deck 
selection part 10, so that the outputs Q and Qof the J/K flip-flop again 
become HIGH-level and LOW-level, respectively, and the A-deck goes into 
the playback-mode and the B-deck changes to the PAUSE-mode, in similar 
manner as mentioned above, thereby playing the tapes in both decks of the 
double deck in parallel. 
As mentioned above, the present invention has the effect that the tapes in 
both decks of the double deck can be played in parallel, so that the user 
can listen to the voice signal of the other tape in the B-deck in turns 
when an unrecorded blank part is detected on listening to the audio sound 
of the tape in the A-deck. 
The invention is in no way limited to the embodiment described hereinabove. 
Various modifications of the disclosed embodiment as well as other 
embodiments of the invention will become apparent to persons skilled in 
the art upon reference to the description of the invention. It is 
therefore contemplated that the appended claims will cover any such 
modifications or embodiments as fall within the true scope of the 
invention.