JPS61140257A - Data communication mode automatic selection system - Google Patents

Abstract

PURPOSE:To switch a data line terminator to the DCE/DTE mode by switching automatically an input/output signal line of the data line terminator depending whether an input voltage of a reception signal voltage detecting circuit is within a prescribed voltage or at the outside of the range. CONSTITUTION:When a reception signal voltage at the input terminal of a receiver 11 is measured by a reception signal voltage detecting circuit 14, the reception signal voltage is <=-3V or >=+3V according to the specification. Thus, the circuit 14 detects it in such a case, its built-in relay 21 is inactivated and contacts 12, 13 are brought into the position shown in dotted lines. If the received signal voltage is between -3V-+3V by the decision of the circuit 14, the built-in relay 21 is activated and the contacts 12, 13 are thrown to the position shown in solid lines.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a data communication device, and in particular, the present invention relates to a data communication device, and in particular, by automatically switching the same data line termination device, when it is configured, it is a data line vA termination device, and when it is configured, it is a data line termination device. Automatic data communication mode selection method for operating as a terminal device % type % When using a data line termination device in a private exchange,
When a data line termination device is used, it is sometimes used as a data line termination device, and when it is used as a data terminal device, it is sometimes used as a data terminal device, but conventionally, it was necessary to manually switch the external connection line each time. Improvement was strongly desired.

[Conventional technology]

When data terminal equipment (hereinafter referred to as DTE) is connected to a transmission line to exchange data with other devices, if the transmission line is an analog transmission line, a modem is installed between the DTE and the transmission line. If the transmission line is a digital transmission line, a home line termination unit (hereinafter referred to as DSU) is used.
(abbreviation for service unit).

The transmitting end of the modem modulates and demodulates the data signal from the DTE, converts it into a telephone line band, and sends it out to the transmission path, and the receiving end performs the inverse conversion.

At the transmitting end of the DSU, the data signal from the DTE is synchronized with the network clock, and synchronization bits and control bits are added to the data signal to create a bearer frame structure, and then a signal suitable for transmission within the city (bipolar signal) and sends it out to the transmission path, and the receiving end performs the inverse conversion.

Note that the modem and DS[J are collectively referred to as data line terminating equipment (hereinafter referred to as DCE).

The connection condition between CE and DTE is DTE/D like this.
It is called a CE interface, and the DTE/DCE interface has mechanical connection conditions, electrical connection conditions, and logical connection conditions.

Electrical connection conditions include v, 2 days, ■, 10, ■, 11, ■
, 35, etc.

Of the above, 2.28 is the mainstream of conventional DTE/DCE interfaces, and is an interface suitable for interconnection circuits operating at data signal speeds of 20 Kbit/s or less. Note that V, 2B has approximately the same specifications as R3232C.

FIG. 3 is a diagram showing an example of a case where a data terminal device is connected to a private exchange.

In the figure, 1 is a private exchange, 2a and 2b are DTE, 3 is a telephone, and 4a, 4b, and 4c are DCE.

5 is a modem, and 6 is a central office line. The same symbols represent the same objects throughout all the figures below.

When connecting the DTEs 2a and 2b to the private exchange 1, they are connected via the DCEs 4a and 4b, respectively. In this case, the electrical condition between DTE2a and DCE4a is V.
, 28 (or R3232C). DTE2b
The electrical conditions between and DCE4b are also the same.

The above connection allows the DTE 2a and DTE 2b to communicate data with each other.

When the DTE 2 a communicates with an external DTE, it is connected to the modem 5 via the DCE 4 c and then connected to the central office line 6 as shown in the figure. In this case, the way the DCE4 is used differs between when communicating within the premises and when using it via a central office line.

In other words, although they are the same data line terminal equipment, D
The CE 4a (same as the DCE 4b) operates as a data line terminating device for the DTE 2a, while the DCE 4c operates as a DTE for the modem 5. Moreover, in DCE4a and DCE4b, the X terminal is an input terminal and the X terminal is an output terminal, but in DCE4c, the X terminal is an output terminal,
The X terminal is the input terminal.

Therefore, the external connections must be changed depending on whether the same data line termination device is used in DCE mode or DTE mode.

In order to switch the data line termination device to DCE/DTE mode like this, conventionally, the switching was done manually using a cross patch cable.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic DTE/DCE mode selection method that eliminates the drawbacks of the above-mentioned conventional methods and automatically switches a data line termination device to the DCE/DTE mode.

[Means for solving problems]

A means for solving the problem is to connect a received signal voltage detection circuit to the input terminal of the receiving circuit of the data communication device in a data communication device that has a plurality of electrical connection conditions, and to detect the received signal voltage. This is achieved by automatically switching the input and output signal lines of the data line termination device depending on whether the input voltage of the circuit is within or outside a predetermined voltage range.

[Effect]

According to the present invention, the received signal voltage at the input end of the receiving circuit of the data line termination device having electrical connection conditions of
Since the received signal voltage at the input terminal drives the relay and automatically switches between the receiving circuit and the transmitting circuit of the data line terminating device, there is an effect that there is no need to switch external wiring as in the conventional case.

[Embodiment] Fig. 1 is a diagram showing an embodiment of the DTE/DCE mode automatic selection method according to the present invention.

In the figure, 10.15 and 15゛ are drivers, respectively.
．． 16 and 16° are receivers, 12 and 13 are switching contacts, 14 is a received signal voltage detection circuit, and 21 is a relay built into the received signal voltage detection circuit 14.

The present invention will be described in detail below with reference to the drawings.

In Figure 1, the left side of the dotted line is DCE, and the right side of the chain line is D
TE or modem, both X and X terminals are DCH
The terminal C is the output terminal of the DTE, the D terminal is the input terminal of the DTP, C' is the input terminal of the modem, and D' is the output terminal of the modem.

(2) According to the 28 Ink Face standard, the open circuit voltage of the receiving circuit is 2.2 or less, and there is a standard that the signal voltage is +3 V or more or -3 V or less in normal use.

Therefore, ■, DCE that meets the standards of 28 interfaces.
The signal voltage at the input end of the receiver 11 under normal use is above +3V or below -3V.

A DTE that also meets the standards of the V.28 interface.
The signal voltage of the D input terminal in normal use is +3V or more,
Or it is -3V or less.

Now, we will discuss the case where the DCE on the left side of the dotted line is used as a DCE, that is, the case where it is used in connection with a DTE.

According to the present invention, as shown in FIG. 1, terminals X and C are connected, and terminal y and terminal RI are connected. Furthermore, switching contact 12.1
Reference numeral 3 indicates a contact point of a relay 21 built into the received signal voltage detection circuit 14, which is normally located at the contact position shown by the dotted line.

The signal output from the driver 15 of the DTE passes through the terminal X in the DCE and the switching contact 12 according to the invention and enters the receiver 11. A received signal voltage detection circuit 14 is connected to the input of the receiver 11 .

In this state, when the received signal voltage at the input terminal of the receiver 11 is measured by the received signal voltage detection circuit 14, the received signal voltage is less than -3V or more than +3V according to the above regulations. Therefore, at this time, the received signal voltage detection circuit 14 detects this, and the built-in relay 21 becomes inactive, and its contacts 12 and 13 assume the contact positions shown by dotted lines.

At this time, if the received signal voltage detection circuit 14 determines that the received signal voltage is between 13V and +3V, the built-in relay 21 is activated, and the contacts 12 and 13 are activated. The contact position changes to the one shown by the solid line.

Next, when connecting to a modem, connect terminals X and C', and connect terminals y and D°.

In this case, the input of the modem's receiver 16° is connected to the terminal The received signal voltage detection circuit 14 detects this, puts the relay 21 into an operating state, and drives the switching contacts 12 and 13 to the contact position shown by the solid line.

As a result, the output of the driver 10 is the switching contact 12, terminal
is connected to the input of the modem's receiver 16,
The output of the modem driver 15 is connected to the input terminal of the receiver 11 through the terminal y and the switching contact 13.

Therefore, the received signal voltage at the input end of the L/receiver 1 becomes less than -3V or more than +3V again. In this case relay 21
will not recover.

The outputs of the other pair of signal lines to be switched at this time are connected, but according to the standard, the circuit will not be destroyed.

FIG. 2 is a diagram showing an embodiment of a received signal voltage detection circuit according to the present invention.

In the figure, 17 and 18 are comparators, 19 is an OR circuit, and 2
0 is a flip-flop circuit, 22 is an inverter, and 23 is an AND circuit.

A reference voltage of +3■ is applied to one input terminal of the comparator 17, and a reference voltage of 13■ is applied to the tenth input terminal of the comparator 18, respectively. Comparator 17 input terminal and comparator 1
One input terminal of 8 is connected to the receiver 11 of the DCE.
Connect to the input end of the

When the received signal voltage (signal voltage at the input terminal of the DCE receiver 11) is +3V or more, the output of the comparator 17 is “1”.
”, and when the voltage is below -3V, the output of comparator 18 is 1.”
becomes.

Therefore, the output of the OR circuit 19 becomes "1", and no clock is supplied to the flip-flop circuit 20, so that the output is always "1".
0'' state, and the relay 21 remains inactive. Its contacts 12 and 13 are in the contact positions shown by dotted lines.

When the received signal voltage is between +3y and -3■, both the output of comparator 17 and the output of comparator 18 are "0".
It is.

Therefore, the output of the OR circuit 19 becomes "0", and when the clock enters the flip-flop circuit 20', it is inverted to "1".
Relay 21 is activated and its contacts 12, 13 are in the contact position shown by solid lines.

After this, the received signal voltage becomes more than +3v or less than -3v, so no clock is supplied to the flip-flop circuit 20, and the relay 21 continues to operate.

〔Effect of the invention〕

As described above in detail, the present invention has the great effect of automatically switching the data line termination device to the DCE/DTE mode.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of an automatic DTE/DCE mode selection system according to the present invention. FIG. 2 is a diagram showing an embodiment of a received signal voltage detection circuit according to the present invention. FIG. 3 is a diagram showing an example of a case where a data terminal device is connected to a private exchange. In the figure, ■ is a private exchange, 2a and 2b are each DTE, 3 is a telephone, 4a, 4b, and 4C are each DCE, 5 is a modem,
6 is a central office line, 10.15 and 15' are respective drivers, 1
116 and 16゛ are receivers respectively, 12.13 is a switching contact, 14 is a received signal voltage detection circuit, 17.18 is a comparator, 19 is an OR circuit, 20 is a flip-flop circuit, 21 is a built-in received signal voltage detection circuit 14 relay,
22 is an inverter, and 23 is an AND circuit. Kaya 1st 'f-2nd grass 3 fields

Claims (1)

[Claims] In a data communication device having a plurality of electrical connection conditions, a received signal voltage detection circuit is connected to the input end of the receiving circuit of the data communication device, and the input voltage of the received signal voltage detection circuit is within a predetermined voltage range. Depending on whether there is or is out of range,
An automatic data communication mode selection method characterized by automatically switching input and output signal lines of the data line termination device.