JP2517889Y2 - Interface device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an interface used for wiring between boards (harness) between circuit boards in an electronic device or a transmission cable between devices.

(B) Conventional technology A plurality of circuit boards are placed inside an electronic device such as a VTR, and if a unidirectional harness is assigned for each signal between these boards, an extremely large number of harnesses are required. . Therefore, as the simplest method of reducing the number of harnesses, for example, as shown in Japanese Patent Application Laid-Open No. 1-129689 (H04N 9/04), bidirectional coaxial cables are used to connect the boards. Is effective.

(C) Problems to be Solved by the Invention It is impossible in terms of cost to use an expensive signal line such as a coaxial cable for transmitting signals between a plurality of substrates.

(D) Means for Solving the Problem In the present invention, the collector is coupled to the power supply line through the resistor (R3), the emitter is coupled to the ground through the resistor (R4), and the base is coupled to the capacitor (C1). A transistor (Q1) coupled to a signal source for transmission via a cable, a cable coupled to an emitter via a capacitor (C2), biasing means for applying a DC bias to a base, and a signal source of a capacitor are coupled to each other. The switch means is inserted between the side and the ground and is controlled to open / close according to the transmission or reception mode. In the transmission mode, the switch means is opened, and in the reception mode, the switch means is closed and the resistance (R3) The feature is that the received signal is extracted from the voltage at both ends.

(E) Operation Since the present invention is configured as described above, bidirectional signal lines can be formed without using expensive and special signal lines such as coaxial cables, and the number of cables or harnesses can be reduced.

(F) Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a main part of this embodiment. The interface circuit (1) includes transistors (Q1) (Q2) (Q3),
It consists of resistance (R1) (R2) (R3) (R4) (R5) (R6) (R7), capacitor (C1) and switch (SW). The collector of transistor (Q1) is connected through resistance (R3). It is coupled to a power supply (Vcc), the emitter is coupled to ground through a resistor (R4), and the base is coupled to a capacitor (C1). In addition, the base is connected to the power supply (Vc
c) and is also connected to the ground via a resistor (R2).

The collector of the transistor (Q2) is connected to the power supply (Vcc), the emitter is connected to the ground via the resistor (R6) and the output terminal (2), and the base is connected to the collector of the transistor (Q1). Has been done.

The collector of the transistor (Q3) is coupled to the base of the transistor (Q1) via the capacitor (C1), the emitter is coupled to ground, and the base is connected to the power supply (Vcc) via the resistor (R7) and switch (SW). Are combined.

(3) is a signal source for transmission, which is coupled to the base of the transistor (Q1) via the resistor (R5) and the capacitor (C1).

Reference numeral (4) is a cable, which is coupled to the emitter of the transistor (Q1) via the resistor (R8) and the capacitor (C2).

The other end of the cable (4) opposite to the one to which the resistor (R8) is connected is provided with an interface circuit (10) having exactly the same configuration as the interface circuit (1) as shown in FIG.
Are joined in pairs. However, the open / closed state of the switch (SW) is completely opposite in both interface circuits.

Next, the circuit operation of each part will be described. First, the case where a signal is transmitted in the direction of arrow A of the cable (4) will be described in detail. First, switch (S) of the interface circuit (1)
When W) is set to the transmission mode, that is, the open state, the transistor (Q3) is turned off, and the transmission signal (V1) from the signal source (3) passes through the output resistor (R5) and the coupling capacitor (C1). After that, it is input to the base of the transistor (Q1). At this time, since a predetermined DC bias obtained by being divided by the resistors (R1) and (R2) is applied to the base of the transistor (Q1), this DC bias is superimposed on the signal (V1) and the signal (V1) is superimposed. V1) is output from the emitter of the transistor (Q1) via the emitter follower, the AC component is cut by the capacitor (C2), passes through the cable (4) via the resistor (R8), and passes through the interface circuit (10).
Be transmitted to.

Also, when transmitting the cable (4) in the direction of arrow B, if the switch (SW) of the interface circuit (1) is set to the receiving mode, that is, the closed state, the transistor (Q3) is
In the ON state, the capacitor (C1) functions as a bypass capacitor and becomes an extremely low impedance in terms of AC. Here, the capacitor (C1) is set to a capacitance value that provides a sufficiently low impedance even at the lower limit value of the frequency that is actually transmitted. As a result, the transistor (Q1) operates as a grounded base amplifier, and the signal (V2) sent via the cable is input to the emitter of the transistor (Q1) through the resistor (R8) and the capacitor (C2). And the resistance (R
The voltage of the same phase as the input will be amplified and appear at both ends of 3). Therefore, the receiving signal (V2) is output to the output terminal (2) via the emitter follower consisting of the transistor (Q2) and the resistor (R6). Be guided. At this time, resistors (R8) and (R3)
The ratio to and becomes the amplifier gain. Therefore, when it is necessary to change the level at the time of transmission, both resistance ratios may be set arbitrarily. On the other hand, on the interface circuit (10) side, the switch (SW) is
If the closed state is reversed, that is, if the interface circuit (1) is in the transmission mode, the switch (SW) of the interface circuit (10) is closed to set the reception mode. If the interface circuit (1) is in the reception mode, By setting the switch (SW) in the open state to the transmission mode, bidirectional signal transmission becomes possible.

The resistor (R8) and the capacitor (C2) may be connected in series to the cable (4) on one side.

(G) Effect of the Invention As described above, according to the present invention, bidirectional signal transmission of analog signals can be performed with an extremely simple circuit configuration and at low cost, and the transmission medium itself can be significantly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS All the drawings relate to an embodiment of the present invention. FIG. 1 is a circuit diagram of a main part of an interface circuit, and FIG. 2 is an explanatory diagram of a signal transmission system. (1) (10) …… interface circuit, (4) …… cable, (3) …… signal source, (2) …… output terminal.

Claims (1)

(57) [Scope of utility model registration request] 1. A collector is coupled to a power supply line through a first resistor (R3), an emitter is coupled to ground through a second resistor (R4), and a base is a first capacitor (C1).
Transistor (Q1) coupled to the signal source for transmission via
A cable coupled to the emitter via a second capacitor (C2), bias means for applying a DC bias to the base, and a side of the first capacitor (C1) to which the signal source is coupled. A switch means which is inserted between a switch and a ground and is controlled to open and close in accordance with a transmission or reception mode. The switch means is opened in a transmission mode, and the switch means is closed in a reception mode. An interface device that extracts a received signal from the voltage across a resistor (R3).