JPS61121628A - Signal transmitter - Google Patents

Abstract

PURPOSE:To expand the transmission distance without mis-judging a signal level by transmitting a predetermined signal from a relay station to a remote relay station as the method discriminating whether or not the signal level change of a signal transmission line is due to a loop back signal or not for a prescribed period after switching in the relay station at the center unit side. CONSTITUTION:The propagation delay between an output signal Q2 of a comparator 54 and an output signal VY of a delay circuit 8 is expressed in equations I, II. Thus, when a transistor (TR) 3 of a relay station 5A is switched from ON to OFF, a voltage Vx across a resistor 51 is decreased, an output signal C of a differential amplifier 52 goes from H to L level, and the output signal Q2 of the comparator 54 changes from L to H level. The output signal VY of the delay circuit 8 changes from L to H level after a time delay expressed in an equation I. Thus, since one input of an AND circuit 55 is at an L level for a period of time delay, an output signal Q3 goes to an L level independently of the output signal Q1 of the comparator 53 and the result is transmitted to a remote relay station via an E/O converter 56 and a relay signal line 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a signal transmission device applied to, for example, a remote control system that exchanges digital information and controls equipment etc. by multiplex transmission.

(Prior Art) In signal transmission devices, there has been a desire for an inexpensive signal path extension device for expanding the communication distance. In addition,
When a signal path is provided outdoors, the electromagnetic environment is poor and there is a risk of intrusion of various noises, so it has been desired to use optical fibers to improve noise resistance.

FIG. 1 is a block diagram showing an example of the configuration of a conventional extension device designed to realize such a request. 1st
As shown in the figure, between the signal path 2 on the center unit side to which the terminal unit 10 is connected and the extension signal path 3 to which the terminal unit 11 is connected, the center unit side relay station 5 and the remote relay A station 6 and a relay signal path 4 are provided. Here, it is assumed that the relay signal path 4 is composed of an optical fiber 4a and an optical fiber 4b, and the center unit l is connected to the power source Vc in order to send the transmission data rQJ or "1" to the signal path 2. A current is supplied to the signal path 2 through the resistor R1 which is connected to the signal path 2. In addition, in order to create a communication control signal, the transistor TRI is turned on with the signal QO.
Or turn it off.

The terminal unit 10 has a resistor R and a transistor TR2 for outputting data to the signal path 2, and controls the transistor R2 to turn on and off based on the output signal QIG.

The remote relay station 6 includes an O/E converter 87 for transmitting the signal from the optical fiber 4a to the extension signal path 3 as an electrical signal.
．． It has a power supply Vc, a resistor R1, a transistor TR4, and a comparator B3 and an E10 converter 6B for transmitting an electrical signal from the extension signal path 3a to the relay signal path (optical fiber 4b) as an optical signal. .

The data rlJ of the signal Q1 created by the ONI transistor TR2 of the terminal unit 10 is transmitted to the relay station 5. The signal is transmitted to the extension signal path 3 via the optical fiber 4a and the remote relay station 8, and reaches the terminal unit 11. Conversely, the data "1" signal on the extension signal path a created by turning on the transistor TR5 of the terminal unit 11 is transmitted via the remote relay station B, the optical fiber 4b, and the relay station 5.
The transistor TR3 is turned on and the signal is transmitted to the signal path 2.

A relay station 5 is connected between the signal path 2 and the relay signal path 4. The signal from the signal path 2 becomes one input to the comparator 53, and its level is compared with the comparison voltage Vsl to become an output signal Q1, which becomes one of the inputs to the AND circuit 55. On the other hand, the voltage Vx across the resistor R51 is transmitted to the differential amplifier 52, and the voltage V! The output signal C changes depending on the magnitude of , and becomes one input of the comparator 54 , and becomes the signal Q 2 by comparing the level with the comparison voltage Vs 2 , and becomes the other input of the AND circuit 55 . The output signal Q3 of the AND circuit 55 is transmitted to the signal path axis via the E10 converter 5B and transmitted to the remote relay station 8.

Signal Q6 from remote relay station 8 is transmitted to O/E converter 57 in relay station 5 via E10 converter 8B and signal path 4b, becomes signal Q7, and is used for switching transistor TR3.

Next, the operation will be explained.

First, we will explain the part corresponding to the timing of section #l in FIG. ) is close to Ov and smaller than the comparison voltage Vat, and the output signal Q of the comparator 53
1 is the "H" level. Also, the voltage V! across the resistor R51! also has a value close to Ov, the output signal C of the differential amplifier 52 is smaller than the comparison voltage Vs2, and the output signal Q2 is r
It becomes HJ level. Therefore, the output signal Q3 of the AND circuit 55 becomes rHJ level during the period Q3,1-Q3,2, and is transmitted to the remote relay station 6 via the E10 converter 5B and the signal path 4a. Therefore, this period Q3, 1-0
3.2, the output signal Q4 of the O/E converter 67 in the far relay station 6 also becomes "H" level, and the transistor TR4
ON, the voltage Q5 of the extension signal path 3 is during the period Q5,1-
Q5,2 becomes "L" level, and the state of the signal path 2 is transmitted to the extension signal path 3.

When the transistor TR2 of the terminal unit 10 is ONI, the "L" level state of the signal path 2 is transmitted to the extension signal path 3 in the same manner as described above.

The transistor of center unit 1 is in period Q0.2-Q0
, 3 from ON to OFF, the signal Vin of the relay station 5 increases and becomes larger than the comparison voltage Vsl, and the output signal Q1 of the comparator 53 becomes "L" level, AN
The output signal Q3 of the D circuit 55 becomes "L" level. Therefore, the signal Q4 of the far relay station 6 also becomes "L" level, the transistor TR4 is turned off, and the voltage Q5 of the signal path 3 becomes the rHJ level in the section Q5,2-Q5.3, which matches the state of the signal path 2. do.

Therefore, by appropriately selecting the ON and OFF periods of the transistors TRI and TR2, the binary information of data rOJ or "1" can be transmitted from the signal path 2 side to the extension signal path 3.

Next, the part of one period #2, that is, the signal transmission in the opposite direction will be explained. Transistor TR of terminal unit 11
5 is turned on in the period Qll, 4-Qll, 5, the voltage Q5 of the signal path 3 becomes "L" level in the period Q5, 4-Q5, 5, and the comparison voltage Vs3 of the comparator 63
Therefore, the output signal QB is at the rHJ level, which is transmitted via the E10 converter 8B and the signal path 4b to the 0/E converter 57 of the relay station 5, and the output signal Q7 is transmitted during the period Q7, 3-Q7, At 5, the level becomes "H", and the transistor TR3 is turned on. At this time, when the transistor TRI of the center unit 1 and the transistor TR2 of the terminal unit 10 are OFF, the resistor R51
The voltage VX across the terminal is determined by the formula 6% [i-value: current flowing through resistor R51.

However, here, the resistance of the signal path, the collector-emitter voltage of the transistor TR3, etc. are ignored for the sake of simplicity, but the same can be said when they are taken into consideration. R1)) R51) Also, when the transistor TRI or the transistor TR2 is ONt, the voltage V! is given by equation (2).

Vx-0(2) Note that the voltage V! due to the drop voltage of resistor R51 and transistor TR3. When there is a possibility that vx may occur, it is possible to insert a diode or a fixed voltage diode in series with the resistor R51 of the relay station 5 to prevent vx from occurring due to the drop voltage of the resistor B or transistor.

Therefore, in the differential amplifier 52, the output signal C is set to the comparison voltage Vs2 for the value of VK shown in equation (1).
For the value of VX shown in equation (2), by setting the signal C to be smaller than the comparison voltage Vs2, the output signal Q2 of the comparator 54 can be set to Vx
can be controlled according to the value of . That is, as shown in FIG. 2, in the period C4-05, the transistor T
Among RI, TR2 and TR3, transistor TR3
When only is ON, the value of voltage Vx is during the period Vx, 4
−Vx, 5, the output signal Q2 of the comparator 54
is the rLJ level in the period Q2,4-Q2,5,
The output signal Q3 of the AND circuit 55 is divided into periods Q3.4-Q3,
8, it is possible to set the level to "L", thereby preventing a communication failure state due to the loopback signal going around.

Further, if the transistor TR5 of the terminal unit 11 is turned from ON to OFF after timing Qll,5, both the signal path 2 and the extension signal path 3 are in the "H" level state.

As explained above, in Figure 2, sections Han 1 and #
2 means the data “0” and “1” of the transmission signal (or rlJ
and "0"), it is clear that communication between the terminal units 10 and 11 is occurring normally via the relay stations 5 and 6.

As already mentioned, the so-called pulse width modulation method, in which a binary signal is expressed by the length of the pulse width at the rLJ level, has been adopted as the form of the transmission signal, but this device can be used for half-duplex and full-duplex methods. It is clear that the present invention can be used as a relay device for a signal path in a general data transmission system.

That is, although FIG. 1 shows an example of application to pulse width modulation, it goes without saying that it can also be applied to cases where I/L (of a signal line) is transmitted in a synchronous or asynchronous manner.

However, the above-described signal transmission device has the following drawbacks. In other words, when a signal changes from a 1 or 0 level to a 0 or l level in a signal path, the current and voltage in the signal path change smoothly or oscillatingly depending on the circuit constants, so the signal changes as shown in Figure 2. In cases such as No. 3R11J (details will be described later), the operation is normal, but in cases such as No. 3R11J (details will be described later), it is due to vibration. Or, when a 0 level signal is generated, the LJ level signal is transmitted to the extension signal path 3, and the loop The back signal changes the signal path from "H" to "L" level again. Since it is the "L" level generated by the loopback signal, the rIl level signal is transmitted to the extension signal path 3, the loopback signal becomes rHJ level, and the signal path changes from "L" to "H" level. , due to the vibration, becomes "L" again. Therefore, the change in rHJ and rL causes the center unit 1 or terminal unit 10 .
11 is repeated until it generates an "L" level signal, resulting in abnormal operation.

This will be explained in detail using FIG.

FIG. 3 is an example of a timing chart of the transmission signal of the device shown in FIG.
This corresponds to around up to in, 5.

In FIG. 3, when the transistor TR3 is turned off at point a, the signal ViN on the signal path 2 becomes the comparison voltage V of the comparator 53.
After crossing sl at point a, it may descend at point b and cross it again at point 0. Voltage V across the resistor 51! falls to the "H" level at point a, and the signal Q2 becomes the "H" level, which is input to one side of the AND circuit 55. On the other hand, the output signal Q+ of the comparator 53 becomes "H" level between be and e, and the output signal Q3 of the AND circuit becomes rHJ level between bxc and is relayed to a long distance via the E10 converter 56 and the relay signal path 4a. The signal is transmitted to the relay station 5 as a loopback signal Qt, and becomes rHJ level between de and e. Transistor TR3 is ON between d”e, signal path 2a-2b
The signal Vi on the signal path 2 is short-circuited through the resistor 51.
n becomes "L" level between dNe. This Vin's "L"
” level is set by the loopback signal to transformer TR3.
is generated by turning ON, the voltage Vx across the resistor 51 becomes "H" level between de and e, signal Q2 becomes rLJ level between ANe, and "L" level between de and e of signal Vin. '' level is not transmitted to the distant relay station. After the @ Vfn exceeds the comparison voltage Vsl at point e, it oscillates due to the circuit constant of signal path 2, and falls below the comparison voltage Vsl again at point f.

The subsequent operation is the same as that at point b, and the same operation is repeated, which becomes a hindrance to signal transmission.

C. Object of the Invention] An object of the present invention is to provide a signal transmission device that solves the above-mentioned problems and can extend the transmission distance without erroneously determining the signal level.

[Key points of the invention]

The present invention provides a method for determining whether the signal level of a signal path is due to a loopback signal during a certain period after switching in a relay station on the center unit side. This system is designed to ensure reliable signal transmission by transmitting a predetermined signal from the same relay station to a distant relay station.

[Embodiment of the Invention] FIG. 4 shows a block diagram showing an example of the configuration of the relay station 5 of the invention.

Relay station 5 of the conventional example (see FIG. 1) and relay section 5A of the present invention
The difference is the presence or absence of a delay circuit. The other components are the same as those in FIG. 1, and are therefore omitted from illustration.

! In the relay station 5A shown in FIG. 4, there are a resistor 5], a diode 58, and a transistor TR3 between the signal paths 2a and 2b, and the voltage Vll across the resistor 51 is input to the differential amplifier 52, and its output signal is input to the comparator 54. This is one of the inputs. The output signal Q2 of the comparator 54 is input to the delay circuit 8,
The output signal vy becomes one of the inputs of the AND circuit 55. The voltage Vin between the @ channels 2a and 2b is compared with the comparison voltage V+1 by the comparator 53, and its output signal Q+ becomes another input of the AND circuit 55. In the AN[1 circuit 55, the output signal vy of the delay circuit 8 and the output signal Q of the comparator 53
An output signal Q3 is created from s. Output signal Q3 is E1
The signal is transmitted to the remote relay station 6 via the 0 converter 5B and the relay signal path 4a.

On the other hand, a loopback signal Q7 is sent from the remote relay station 6 via the relay signal path 4b and the O/E converter 57.

Transistor TR3 is driven by loopback signal Q7 and connects signal paths 2a, 2b to resistor R and diode 58.
A signal is generated in the signal path 2 by a loopback signal by short-circuiting the signal through the signal path 2.

The function of the relay station 5A is to transmit the signal on the signal path 2 generated by the center unit 1 or the terminal unit IO to the extension signal path 3 via the relay signal path 4a, The signal on the signal path a including the signal generated in step 11 is received as a loopback signal via the relay signal path 4b, and a signal is created on the signal path 2.

The delay circuit 8 includes an inverter 81 . connected to the output of the comparator 54 . Transistor 82. Resistors 83, 84, 85. It consists of a capacitor 8B and a gate 87. If the output signal Q2 of the comparator 54 is at the "L" level, the base current flows through the inverter 81, and the transistor 82 is turned off.
NI, the voltage Vc of the capacitor 8B is a value given by the following equation.

Rd+rd Rd+rd d The value of Vc in equation (2) is close to Ov, and the output signal vy of the gate 87 is at the rLJ level. On the other hand, the comparator 54
If the output signal Q2 of is at rHJ level, the transistor 8
2 is turned off. At this time, the capacitor 8B is charged from the power supply v2 via the resistor 85, the voltage Vc across the capacitor 8B increases, and the output signal vy of the gate 87 is inverted from the rLJ level to the rHJ level.

Output signal Q2 of comparator 54 and output signal vy of delay circuit B
The propagation delay between is expressed by the following equation.

Output signal Q2 goes from L to H.
3) H to L het'dwaKrdcd (4) (
Here: constant) Therefore, when the transistor TR3 of the relay station 5A switches from ON to OFF, the voltage Vx across the resistor 51
decreases, and the output signal C of the differential amplifier 52 changes from "H" to "L".
” level, and the output signal Q2 of the comparator 54 also becomes “L” level.
' to the rHJ level. At this time, delay circuit 8
After the time delay shown in equation (3), the output signal vy of
It will change from "L" to rHJ level. Therefore, during this time delay period, since one of the inputs of the AND circuit 55 is at the "L" level, the output signal Q3 becomes the "L" level immediately after the value of the output signal Q1 of the comparator 53, and the E10 conversion is performed. The signal is transmitted to a distant relay station via the relay signal line 3a and the relay signal path 3a.

The above time delay Td is different from the signal V
Resistor 8 so that it is larger than the time it takes for in to stabilize.
6 and the capacitance Cd of the capacitor 86 may be set.

On the other hand, when the input signal Q2 of the delay circuit 8 changes from rHJ to "L" level, FIJIiret'd is calculated by equation (4).
The zero time delay t'd denoted by the signal i! Since this is the time delay of the signal Q3 transmitted from 32 to the extension signal path 3, it is desirable that the value be as small as possible, and the resistance value rd of the resistor 84 is selected to be a small value.

FIG. 5 is an example of a transmission timing chart of the present invention, and the signal Vin on the signal path 2 is the same as that in FIG. 3 up to the 0 point.

As shown in FIG. 5, the voltage Vx across the resistor 51 is a-a
'The falling edge between the differential amplifiers 52 and 52. The comparator 54 and the delay circuit 8 produce the rLJ level between a and e'' of the signal Q2. The delay time between a and a''' is set by circuit constants Rd, Cd, etc. in the delay circuit 8. On the other hand, signal Q
I becomes the "H level" between b and c ii, but since the signal Q2 is at the "L" level between b and c, the output signal Q3 of the AND circuit 55 remains at the "L" level, and as shown in FIG. It is different from Therefore, the roof'/<tsuk signal Q7 is a
The "L" level that fell at the point is maintained.

[Effects of the Invention] As explained above, according to the present invention, reliable signal transmission can be carried out through an extended transmission line without being affected by the circuit constants of the signal path, and the practical effect is achieved. is large.

[Brief explanation of drawings]

Figure 1 is a block diagram showing an example of a configuration in which a conventional transmission device is applied to a time division multiplex transmission system, Figures 2 and 3 are timing charts of transmission signals of the transmission system in Figure 1, and Figure 4 is a diagram of the present invention. FIG. 2 is a block diagram showing an example of the configuration of the invention transmission device. FIG. 5 is a diagram showing an example of a timing chart of transmission signals of the transmission apparatus of the present invention. 1...Center unit. 10.11...Terminal unit. 2a, 2b... Signal path, 3a, 3b... Extension signal path, 4a, 4b... Relay signal path, 5... Relay right, 8... Long distance relay right, 8... Delay circuit. Figure 2 v, 4 v, . Figure 4 Kinuta

Claims (1)

[Scope of Claims] A signal transmission device in which a center unit and a plurality of terminal units are connected via a signal path and signals are transmitted between the center unit and the terminal units or between the terminal units, comprising: A signal path is connected to a center unit side signal path with one end connected to the center unit, a center unit side relay station connected to the other end of the center unit side signal path, a far relay station provided far away, and both relays. It is extended by a relay signal path that connects the stations and an extension signal path that is connected to the remote relay station, and the center unit side relay station has a signal path of "1" or "0" on the center unit side signal path. means for detecting a level; means for transmitting a signal corresponding to the level detected by the detecting means to the relay signal path; means for changing the level of the signal path on the center unit side to "1" or "0" by the changing means; means for detecting a change in level by the changing means and stopping the transmission of the transmitting means; means for delaying the stop time, and the remote relay station is configured to set the level of the extension signal path to "1" or means for changing the level to "0"; means for detecting the level of "1" or "0" on the extension signal path; and transmitting a signal corresponding to the level detected by the detection means to the relay signal path. 1. A signal transmission device comprising: means.