DE4337593A1 - Multi-frequency method for transmitting alphanumeric messages - Google Patents

Abstract

To transmit alphanumeric messages via telephone connections, modem chips are in most cases needed as ancillary device. To provide for such a transmission by means of DTMF telephone terminals as transmitters and receivers and by means of two groups A and B/B' of a number of frequencies without ancillary device, a method has been created in which the transmitter first sends to the receiver a synchronisation signal which is acknowledged by a receiver ready for text reception, in which then a data format block transmission is carried out which begins with a start-of-text and type-of-information character and is continued with a variable number of information items and which ends with an end-of-text signal after a checksum check. In this arrangement, time blocks with three typical time windows are formed for the frequency changes. The receiver finally sends a positive or negative acknowledgement signal. This provides an economic possibility for the transmission of short text between DTMF telecommunication systems without ancillary devices.

Description

The invention relates to a method of The preamble of claim 1 specified type. It is used in telecommunications systems with multi-frequency Switching (DTMF) usable. Signaling method using alpha characters in such facilities z. B. from DE 37 32 679 and 3823 914 known.

The text transmission via telecommunication communication systems takes place in a generally known manner z. By TELEX, FAX or modem transmission according to the usual switching Procedure in telecommunication communication systems. For this are in addition to the telecommunications communication equipment for the Speech services separate facilities required.

The simplest type of text transfer is that Modem method known with different Transmission speeds is used. This also requires one next to the DTMF receiver Modem module.

The object of the invention is to provide a telephone terminal to use a simple text transmission without For this an additional device to the public Telephone network must be connected. Next should be the Text transmission alpha-numerically between two such Terminal equipment in the send and receive directions possible his. In addition, should from any telephone (also IWV with Switching to DTMF) numeric from a distance Information in the memory of this terminal can be sent.  

This object is achieved with the in the license plate solved by the method described in claim 1.

From the characteristics of the subclaims are advantageous Further developments of the method can be seen.

It has not been possible to date the full alpha character set with simple means and appropriate security too transfer.

The usual transmission protocol of telecommunications Communication equipment allows, in addition to the transmission of alpha characters also save and control characters in shape to send a data block. The procedure intervenes modified transmission method according to a FTZ Standard design 12 R 6.2 back. Part of this design is not, however, the integration into an as in the appendix illustrated transmission protocol.

Because the method is specifically for use with a Short text transmission was provided, was a lesser Transmission speed accepted.

The advantage of the invention is that it is a Text transmission on the simple telephone connection is involved, d. H. despite alpha-numeric text transmission is the Terminal connected as a simple terminal. Another advantage of this specific DTMF transmission is the alpha-numeric character transfer in the range Cityruf.

By using the appropriate data block and the modified transmission method is for the hardware only a DTMF receiver needed. Thus, that allows Method a short text transfer on extra inexpensive way.

The invention is based on an embodiment explained in more detail. In the accompanying drawings show the

Fig. 1 shows a data format of the block transfer.

Fig. 2 is a transmission sequence and Fig. 3 is a character set table.

The text transmission between two subscribers takes place, as shown in FIG. 1, according to the DTMF method FIG. The texts are transmitted in blocks.

Before each text transmission is a synchronization (Code SYN) with the receiver. The recipient acknowledges the Code with ACK. If the code is not acknowledged, then an optional timeout of 2 seconds a new attempt. To three attempts will abort the transfer. Will the Code acknowledged with NAK, the transmission is instantaneous canceled.

The first character behind "Start of Text" is the Information Type. It is sufficient if one type of information, For example, "1" (31h) of the expected DTMF Telephone terminal is supported.

Example: "1" = text → text block follows.

The number of characters between "Start of Text" and "End of text block" is variable. She is at the provided DTMF telephone terminal to max. 150 Limited characters.

The checksum is formed by adding the characters between "Start of Text" and "End of Text-Block". The hexadecimal values for the characters are taken from the ASCII table (see Character Set Table Fig. 3). Transfers from the addition are not taken into account. The checksum is transmitted in hexadecimal. The letters A become. , , F always sent as uppercase letters.

Example:
STX, "1", "TEST", ETB
→ 31H + 54H + 45H + 53H + 54H = 71H
Checksum high = 7
Checksum low = 1

Each data block must be marked with "Acknowledge" or "negative Acknowledge "(ACK / NAK) is acknowledged NAK acknowledges, this must again completely sent become.

Reasons for NAK:

• - wrong checksum
• - Receive error with the DTMF receiver
• - Timeout

For example, if a block of data is NAK three times acknowledged, the transmitter aborts the data transmission.

If a data block is not acknowledged after a timeout of 3 seconds has been sent, the block is sent again. Done again no receipt, the transfer is aborted.

If the receiver does not have a timeout of 3 seconds received complete data block, he sends NAK as a receipt.

The transmission sequence of the data is shown in FIG . The individual characters are generated from the frequencies A, B and A, B.

For example, you can use:

A1 = 697 Hz B1 = B1 '= 1209 Hz A2 = 770 Hz B2 = B2 '= 1336 Hz   A3 = 852 Hz B3 = B3 '= 1477 Hz A4 = 941 Hz B4 = B4 '= 1633 Hz

The character encoding is apparent from FIG. 3. The control and control characters have the following meaning:

The prerequisite DTMF telephone terminal is supported following control and control characters:

LF, ACK, NAK, STX, ETX ETB, SYN, DC1, DC2, DC3

All other control characters are allowed inside and outside a text block is not sent.

The control character LF is only within a text block authorized. It separates the individual lines of the text. The number of characters is before, between and after the LF limited to 20. There can be a maximum of 5 LF in the text block occur.

The control characters ACK and NAK are used to acknowledge the Synchronization and data.  

The control characters DC1, DC2 and DC3 are only for the Announcement mode used. Does the required DTMF telephone Terminal after an announcement ready to receive signaled, a timeout of 17 seconds is started. Becomes within this time received no sign, sends the prerequisite DTMF telephone terminal the control character DC1. If this DC1 is answered with a DC2, extended the timeout is 20 sec. Each additional DC2 is extended the timeout by 20 sec. If no DC2 (or SYN) after a DC1, the readiness to stand by after 3 sec Disconnecting the line ended.

The control character DC3 is used instead of an ACK or NAK sent if the provided DTMF telephone end during a text transmission from the text announcement company in the handset operation has passed.

If the calling party has only one DTMF Touch-tone phone (or a bilingual phone), so he has the ability to call your own number in the DTMF code transfer.

Has the provided DTMF telephone terminal with a Text announcement readiness to receive signals, the Send caller a number in the multi-frequency dialing. Allowed are the following signs:

1, 2, 3, 4, 5, 6, 7, 8, 9, 0, *, #

Does not precede after a timeout of 20 seconds received DTMF telephone terminal, the Line disconnected. After the first digit is a timeout valid for 10 seconds. Will not be a digit in this time received, or 20 digits have been received, so switches off the device and disconnects the line.

Claims (3)

1. A multi-frequency method for transmitting alpha-numeric messages from the input of a first DTMF telephone terminal as a transmitter to the memory of another DTMF telephone terminal as a receiver by means of two groups A and B / B 'of several frequencies, in changing sequences are transmitted, characterized in that for the beginning of a text transmission first by the sender a synchronous signal (code SYN) is sent, which acknowledged by a receiver ready for text reception (code ACK), that thereafter a data format block transfer is performed which begins with Start of Text (Code STX) followed by an Information Type character, then continues with a variable number of n information, and continues with an End of Text Block (Code ETB) hexadecimal checksum for high and low as a check mark and an end of text signal (code ETX) ends that form time blocks for the frequency change with three time windows t in whose first two windows the group A has a constant and the group B / B 'predominantly changing frequency, while the third time window is used as the pause time of both groups, and that within a predetermined time after the data format block transmission from the receiver a positive (Code ACK) or negative (Code NAK) acknowledgment character whose negative form (Code NAK) or its absence causes the transmitter to repeat or abort the transmission. 2. Multi-frequency method for transmitting alpha-numeric Messages according to claim 1, characterized that each four frequencies for the blocks A and B / B 'such combined, that the extended ASCII Character Map is transferable. 3. Multi-frequency method for transmitting alpha-numeric Messages according to claim 1, characterized that of stations with exclusive digit selection after a text message from the recipient indicating the reception willingness to enter a phone number becomes.