DE3119275C2 - Method for recording digital information in the form of signal tones on a recording medium - Google Patents

Abstract

According to the method according to the invention, the recording of digital information on a recording medium takes place immediately after a soundless interval, and at the beginning of the digital information a signal tone with a fixed level is recorded on the recording medium. A soundless interval is preferably set between the signal tone with a fixed level and the start of the digital information.

Description

■ '■ * The invention relates to a method for recording digital information in the form of beeps on a recording medium according to the preamble of the main claim.

With the increasing spread of programmable computers (especially pocket calculators) Tape cassettes for recording programs and control data are used as additional storage media used because they are cheap and widely available. The recording of digital information on however, a fine recording medium intended for acoustic reproduction is not problematic because commercially available tape and / or music playback devices z. B. contain an automatic level equalization circuit to make low volume levels strong and large Amplify volume level less. The automatic compensation is for the recording of audio signals (in broadest sense) and not for the recording of digital information. Therefore the read out Digital information may be in error, particularly with the recording method discussed below II.

For the recording of digital information on a device intended for audio or sound reproduction purposes There are recording media

I. the double frequency method, in which all logic levels "1" are FM-modulated with a first frequency U and all logic levels "0" with a second frequency h; and

II. The single-level frequency method (tone burst method) in which only the one logical level "1" or "0" is modulated with a certain frequency, the other is kept at zero level to determine the Pulse width the pulse dial is counted over a given period and based on the determined Pulse number or time the associated logic level »1« or »0« is recognized.

The aforementioned recording level equalization circuit is responsible for ensuring that the Record the tape sections that should be completely without a signal and e.g. B. reserved for logical "0", unavoidably occupied with a noise signal and therefore incorrectly read as a logical "1". In addition, a defined signal recorded immediately after a soundless interval becomes in its Initial level fluctuates greatly and is distorted; this effect is also disruptive.

The invention is based on the object Specify the method of the type mentioned, which is designed so that even when recording after a sound-free interval in a recording device with automatic level control ensures that the digital information is written at a reproducible level.

The solution according to the invention is briefly reproduced in the main claim. It is characterized by the fact that a signal tone with a fixed level is recorded before the start of the recording of the digital information. By this measure, the level of the auto level is determined in a reproducible manner, so that a digital informa tion can be written ^v from beginning to end with essentially the same "level.

According to an advantageous development, the method is carried out so that between the signal tone with a fixed level and the beginning of the recording of the digital information a signal-free interval on the

, Recording medium is recorded. The Inter-

* vall is so long that the level of the modulation, the is determined by the recorded signal tone, not during the duration of the signal-free interval changes. Such a soundless section is helpful to clearly determine the beginning of the data recording to be able to. An embodiment having the features of the invention is shown below

Yj explained in more detail with reference to a drawing. It shows

Fig. 1 different representations of a digital signal,
F i g. Figure 2 shows a typical arrangement of recorded information;

3 shows a block diagram of a computer with a connected cassette recorder,

F i g. 4 and 5 flow charts for loading and reading • information,

Fig.6 shows an arrangement of an 8-bit code between Data, and

F i g. 7 (a) and 7 (b) representations of recording data with markings or a CC element in FIG Recording.

- «/ Fig. I (a) shows a recorded or on a Tape to be recorded, and this is in Fig. 1 (b) the corresponding from logic levels "1" and "0" are compared with composite digital information, their "O" level for a specified time runs low and level and its logical "1" level consists of five pulses at 5 kHz.

In the example shown in FIG. 2 of an anoi inung (format) of data for a recording on a recording medium for sound reproduction

For this reason, the soundless sections (logic level "0") are labeled IRG \ and IRGi (shorter section). An auxiliary section FS (logic level "1") contains z. B. Recording signals of 250 ms duration and has the task of damaging influences on DATA sections

*> 5 which would otherwise be caused by fluctuations in the recording level due to the above-mentioned level equalization circuit. The output (recording) of section PS limits the

Recording level of section IRGi over its very short duration. In general, the level compensation circuit regulates so slowly that it keeps the recording level over the short section / AG ₂ at the level value determined by the section PS , so that the recording on the DATA sections takes place at this level.

Iu Fig.3 is a conventional computer or computer COM, which contains a microprocessor MP , an input / output unit IO, a read / write memory RAM and a read-only memory ROM , combined with a cassette tape recorder CTR . The units MP, IO, RAM and ROM are connected to one another via an address bus AB, data bus OB and control bus CB . An output signal from a terminal P _{2 of} the input / output unit IO receives a fixed level via resistors and a capacitor and goes as a recording signal into the cassette recorder CTR. During playback, a playback signal from the cassette recorder goes through a capacitor and a Schmitt circuit SS for noise suppression . middle level range to a connection P \ of the input / output unit IO.

'S g The recording of the signal from F i. 2 takes place according to the flow chart in FIG. 4, in which "00" (hexadecimal) or 8 bits all zero in succession over a time Ti (eg 14s) go in series to input P ₂ . Included

-The toneless interval IRG ₁ arises in the time Ti on the tape. At S3 , FF (hexadecimal) or 8 bits, all one, goes out over a time Tz; this creates the T ₂ long auxiliary section. At S ₅ and S ₆ , the toneless section / AC ₂ extending over Tj arises, where T _{3 can be} equal to or longer than Ti , provided that this does not lead to a change in the recording level by the level compensation circuit. After these auxiliary signals have been recorded, message signals corresponding to the desired information sections are transmitted with Si _{via the output P 2} and then a second soundless section TRGi is output at St and S ₃ , which is practically identical to the first. The longer first soundless section ensures the recording of information when the tape starts up and / or serves as a distinguishing feature between a previous and a new recording. The longer second soundless section marks the end of the recording compared to another. The lying directly behind the auxiliary section short soundless portion / AG ₂ is used to distinguish between the soundless portion and the beginning of data.

Information that has already been recorded is read out according to the flow chart in FIG. If a soundless signal is reproduced from the cassette recorder, which z. B. is more than a few seconds long, it is first decided with (n \ - * W ₂ ) whether it falls into the auxiliary section. Both findings or decisions are dependent on the logic level value at input P \. Any initial distortions present are reduced in the auxiliary section PS (time T _{2) <uark.}

Real signals come in Fig. 2 at / 1. After the auxiliary section has been recorded, the cassette recorder is ready to record incoming data after time T2 has elapsed (m - m). If at time h the auxiliary recording

ί section recognized, then the recorder is ready to record the data inputs. i ₂ is now T2 later than r ,. That is, the tape recorder is ^; n Readiness, and as soon as the data begins, they are entered and converted or coded in parallel in series, and the

The set result is loaded into a corresponding location in the RAM.

6 shows the structure of an 8-bit code signal within the data. The signal sequence begins with a start bit 5 / (level "1"), a stop bit Sf (level "0"), upper 4-bit data D \ and lower 4-bit data D ₂ , the stop bit Bits are followed by the 2-bit long data D ₂ so that the coded signal can be stored in a memory location after its input has ended and the input of the start bit for the next coded signal is prevented until the storage process is complete.

As the encoded 8-bit signal in halves of 4 bits

is divided, the period between the start bit

. and the stop bit is shorter and the operational reliability of the cassette recorder against changes in tape speed is greater. Because the start bit is logic "1", the tape is recorded with at least every sixth bit, even if Di and D _{2 are} all zero. Therefore, the level equalizing circuit cannot perform the recording

3.0 interfere with the recording operation by noticeably increasing the recording level.

The exemplary embodiment of a data recording shown in FIG. 7 (a) contains markings DATA for data, LB for a title and CC for the type and length of the data. The soundless section IRG3 is longer than

IRG ₂ , so that the start of data does not fall within a period of time when a decision is made as to whether the title selected by the operator corresponds to the title LB on the tape. The soundless section IRG ₃ is longer than

«0 the response time of the level compensation circuit, and am

- The start of the data is the auxiliary section PS.

The in F i g. The content of a CC mark shown in FIG. 7 (b) from FIG. 7 (a) contains a "secret" bit because the subsequent data are confidential. In this case it is

• »5 every dubbing to an external recording medium impossible, however, loading into the computer. Should a bit be mistakenly marked as confidential or a If such a bit is misread, hardly any confidential information will be disclosed.

So the inventive method for recording of digital information begins with a soundless section and thereby switches adverse influences on the part of a level compensation circuit. With a soundless section between the sound signal a specified level and the start of information recording becomes a certain recording level is set and held while the section of digital data is being recorded.

For this purpose 4 sheets of drawings

Claims (2)

Patent claims: 1. A method for recording digital information in the form of signal tones on a recording medium using a recording device with automatic level control, in which method the digital information is recorded after a tone-free interval, characterized in that before the beginning of the recording of the digital information (DATA) a signal tone (PS) is recorded with a fixed level, which determines the level of the automatic level control. 2. The method according to claim 1, characterized in that a tone or signal-free interval (IRG 2) of such a duration (T3) is placed between the signal tone with a fixed Ppgel and the beginning of the digital information that the level of the modulation, which by the pre-recorded signal tone (PS) is set, does not change during this duration (T3).