JPH02136483A - Burglarproof device for vehicle - Google Patents

Abstract

PURPOSE:To ensure safety by receiving the detecting signal of a key detecting means provided to a steering locking device and a starter signal at a time when a starter switch is turned ON by a trigger circuit and generating trigger pulses. CONSTITUTION:In a steering locking device, a key detecting means 10 having a photoelectric conversion means optically reading a key code is provided, and a detecting signal is generated by operating a normal key. When the key is rotated from the steering locking device to the position of start and turned ON, a starter signal is generated and received by a trigger circuit 19 together with a key detecting signal, and trigger pulses are generated. The trigger pulses are applied to a thyristor circuit 104 and a switching circuit, and a vehicle drive control circuit 106 is supplied with power. Accordingly, safety can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-theft device, and particularly to an anti-theft device for a vehicle that prevents the vehicle from operating in the event of theft.

4114 For example, as disclosed in U.S. Pat. No. 3,628,099, a specific electrical resistor is attached to a key for starting a car, and a plurality of contacts provided in a steering lock device of the car are connected. Anti-theft devices that determine the resistance value of this electric resistor between the two are well known. This anti-theft device can operate the starter of the automobile only when the resistance value of the electric resistor is within a predetermined range.

Also, for example, U.S. Patent Nos. 3,634,724 and 3
, 660, 624, etc., also disclose anti-theft devices.

However, in the conventional anti-theft device described above, the control circuit continuously applies an activation signal to the switching circuit that activates the starter motor when the resistance value of the electric resistor falls within a predetermined range. , starts the starter motor, thereby starting the engine. In this case, the battery voltage is normally 12 volts, but since a large current flows to the starter motor due to variations when the starter motor is activated, the battery voltage drops to 5 volts or less. The control circuit is composed of an integrated circuit (IC) that operates at a predetermined power supply voltage, and has the disadvantage that it malfunctions when the battery voltage drops below 5 volts. For this reason, the vehicle could not be safely driven when the starter motor was activated.

On the other hand, vehicles equipped with an automatic transmission are equipped with a shift lock device. This shift lock device prevents erroneous operation that occurs when starting the vehicle.
It has a configuration that allows the engine to be started only when the vehicle is in the parking position. That is, when the shift lever is in a "drive position" or "r-back position" other than the "parking position," operation of the ignition lock device using the key is prevented. When the shift lever is in the "parking position", the ignition lock device can be rotated from the "locked position" to the "on position" using the key.

Conversely, turn the ignition lock device from "r on position" to "
When rotating the key to the "lock position", the key cannot be rotated to the "lock position" unless the shift lever is switched to the "parking position". These operations are performed by a shift lock solenoid device provided adjacent to the shift lever and a key lock solenoid device provided in the steering lock device. However, since these devices are well known, detailed explanation will be omitted.

However, these devices cannot reliably prevent erroneous operation when starting the vehicle, i.e., even if the shift lever is in the "park position", when the key is turned to the "on" position of the ignition switch, Since the shift lock solenoid device is activated, if the shift lever is then rotated to another position other than the "park position" such as the "drive position" or the "rback position" and the key is turned to the "start" position, the starter motor will The vehicle starts suddenly due to the energization. Conventional automatic transmissions have not been able to eliminate this drawback.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vehicle theft prevention device that can prevent the operation of a vehicle in the event of theft and can reliably prevent accidents caused by erroneous operation of the vehicle or malfunction of electronic devices.

The anti-theft device for a vehicle according to the present invention generates a trigger pulse when receiving a detection signal from a key detection means provided in a steering lock device and a starter signal generated when a starter switch is turned on. a trigger circuit;
The vehicle drive control device includes a thyristor circuit having a gate that receives a trigger pulse of the trigger circuit, a switching circuit that is turned on when the thyristor circuit is conductive, and a vehicle drive control device that is supplied with power from a power source when the switching circuit is turned on.

The key detection means includes photoelectric conversion means for optically reading the key code provided on the key. In another embodiment of the invention, the thyristor circuit has a first thyristor and a second thyristor, the anode of the first thyristor is connected to a coil of a relay, and one contact of the relay is connected to a power source. connected, the other contact of the relay is connected to the engine starter, and the anode of the second thyristor is connected to the switching circuit, so that when the switching circuit is on, power is passed from the IL source through the ignition switch to the shift lock control circuit. is supplied, and the shift lever lock device is unlocked by the output of the shift lock control circuit.

1. When the steering lock device is operated with a regular key, a detection signal is generated by the key detection means.

At the same time, when the key is rotated from the lock position of the steering lock device to the start position, a starter signal is generated when the starter switch is turned on. The trigger circuit generates a trigger pulse when receiving the key detection signal and the starter signal.

When the trigger pulse of the trigger circuit is applied to the gate of the thyristor circuit, the thyristor circuit is turned on. Therefore, the switching circuit is turned on, and power is supplied from the power source to the vehicle drive control device through the switching circuit.

The trigger circuit can automatically switch from operating mode to standby mode after generating a trigger pulse with a short pulse width. Further, since power is supplied to the vehicle drive control device from a switching circuit different from the trigger circuit, it is possible to prevent malfunction of the electronic circuit due to a voltage drop in the battery that occurs when the starter motor is activated.

The key detection means provided in the steering lock device optically reads the key code provided on the key through the photoelectric conversion means, and generates an output to the trigger circuit when the read code number corresponds to a predetermined code.

In another embodiment of the invention, the trigger pulse of the trigger circuit is applied to each gate of the first thyristor and the second thyristor of the thyristor circuit. Therefore, when the first thyristor is turned on, the relay is energized and current is supplied to the engine starter. At the same time, the second thyristor is turned on, so the switching circuit is turned on.

Therefore, power is supplied from the power supply through the switching circuit to the shift lock control circuit through the ignition switch, and the shift lever lock device is unlocked by the output of the shift lock control circuit. Therefore, the starter motor of the automobile can be operated, and at the same time, the shift lever can be operated to drive the automobile in a normal state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a vehicle anti-theft device according to the present invention will be described with reference to FIGS. 1 to 10.

First, as shown in FIG. 4, the key detection means 10 selects the two light emitting devices 11 and the light emitted from the light emitting devices 11 and passing through the light guiding member 13 of the ignition key 12 (FIG. 6). four light-receiving sensors 14 to 17 that receive light, a control circuit 18 as a comparison means that generates a coincidence signal when the output of a predetermined light-receiving sensor is received, and a control circuit 1
8, and a trigger circuit 19 activated by a coincidence signal of 8. The key detection means 10 has a photoelectric conversion means for optically reading a key code provided on a key as described later.

As shown in FIGS. 6 and 7, one light emitting device 11 is connected to an ignition key insertion portion 2 of a steering lock device 27.
0, and a pair of infrared light emitting diodes 22 arranged opposite to the ignition key insertion part 20. Also, as shown in Figure 7,
Light receiving sensors 14 to 17 are arranged in a line at positions 90 degrees apart from diode 22 . The ignition key 12 includes a metal key blade 23 and a key blade 2.
3, and a light guide member 13 provided within the head portion 24. The key blade 23 of the ignition key 12 locks the steering lock device 27 when unlocking, as shown in FIGS. 6 and 7.
is inserted into the ignition key cylinder 25 of.

As shown in FIG. 9, the light guide member 13 is made of a light-transmitting resin such as silicone resin or acrylic resin.
A light receiving section 30 formed at one end of 3, and a light receiving section 30 formed at one end of 4.
It has a light guide section 31 branched into two, and four light emitting sections 32 formed at the other end of each light guide section 31. The light receiving part 30 is exposed from the head part 24 on one side of the key blade 23, and receives the light from the infrared light emitting diode 22. 6. Current automobile ignition keys are rotated 180 degrees and inserted into the ignition key cylinder 25. Reversible ignition keys, which can also be used to unlock cars, are often used.

Therefore, even if the ignition key 12 is rotated 180 degrees from the state shown in FIG. A pair of diodes 22 are provided at the layer separation positions.

The light guide portion 31 of the light guide member 13 passes through the head portion 24 and each end face of one light emitting portion 32 is exposed from the linear edge 26 of the head portion 24 . When the ignition key 12 is inserted into the ignition key cylinder of the steering lock device 27 and rotated from the lock position to the start position, the infrared light emitted from the light emitting diode 22 at the start position is transmitted to the light receiving part of the light guide member 13. The infrared light emitted from the light emitting part 32 to the outside of the light guide member 13 is received by the light receiving sensors 14 to 17. In the illustrated example, the light guide part 31 of the light guide member 13 is branched into four parts, and four light emitting parts 32 are provided, but some of the four light emitting parts 32 are selectively cut and a key code is set. be done.

That is, an optical key code is set depending on the presence or absence of infrared light to the light receiving sensors 14 to 17.

As shown in FIG. 4, a power supply positive terminal 40 connected to the positive terminal of a battery (not shown) is connected to the emitter of a transistor 43 via a diode 41 and a resistor 42. The collector of the transistor 43 is a reset circuit 44
It is connected to the reset terminal R of the control circuit 18 via.

A constant voltage diode 4 is connected between the power supply negative terminal 46 connected to the negative terminal of the battery and the emitter of the transistor 43.
7 is connected. Further, the resistor 48 and the other end of the capacitor 53, each having one end connected to the capacitor 45 of the reset circuit 44, are connected to the power supply negative terminal 46. Furthermore, a resistor 50. A capacitor 51 and a diode 52 are connected in parallel. The capacitor 45 and the resistor 50 constitute a pulse shaping circuit, and apply a pulse signal to the reset terminal R.

The trigger switch 55 shown in FIG. 4 constitutes an ignition switch or a starter switch.

When the ignition switch or starter switch is turned on, the transistor 5 is connected through the resistors 56 and 57.
Supply current to the base of 8. A constant voltage diode 59 is connected between resistors 56 and 57. transistor 5
The emitter of transistor 8 is grounded, and the collector is connected to the base of transistor 43 via resistor 60. Further, the base of transistor 43 is connected to the collector of transistor 69. The base of the transistor 69 is connected to the output port 0U of the control circuit 18, and the emitter is grounded. Further, the collector of the transistor 58 is connected to the input port I6 of the control circuit 18. When the transistor 58 is turned on, the input port E is brought to a low voltage level, and the control circuit 18 is switched from standby mode to operating mode for a fixed period of time by built-in timer means. In the operating mode, when a certain period of time has elapsed, the timer means generates an output from output port 0, turning on transistor 69. Therefore, the base potential of transistor 43 decreases and transistor 43 is turned off. Therefore, the control circuit 18 is switched from the operating mode to the standby mode.

The light receiving sensors 14-17 are connected to input ports I, -, of the control circuit 18 via resistors 61-64. Further, each of the light receiving sensors 14 to 17 is connected to the collector of the transistor 43, and the light receiving sensors 14 to 17 are connected to the resistors 61 to 64.
Transistor 4 is connected between resistors 65 and 68 between 4 and 17.
3 collectors are connected. Furthermore, the collector of the transistor 43 is connected via a diode 90 to the power supply input port of the control circuit 18 .

Output ports 0□ and 0. of the control circuit 18. An infrared light emitting diode 22 is connected to each of the infrared light emitting diodes 22 via two amplifiers 70.71 and 72.73. Further, a trigger circuit 19 is connected to the output port 04 via two amplifiers 74 and 75. Further, a port Ps""Ps of a ROM (read only memory) 77 is connected to the ports P1 to P4. The same information as the 4-bit code signal received from the light receiving sensors 14-17 is stored in the ROM 77. The input terminals 11 to Ixa of the ROM 77 are connected to the collector of the transistor 43, and the input terminal 1 of the ROM 77 is connected to the power supply negative terminal 46. Control circuit 1
The input port No. 8 is connected to the power supply negative side terminal 46 via the code registration switch 78.

It is connected to the collector of transistor 43 via resistor 79. In FIG. 4, A and B indicate terminals connected to A and B, respectively.

The control circuit 18 is configured as a one-chip microcomputer, and includes a timer means, a code registration means, and a comparison circuit that receives the code signal stored in the code registration means and the output of the light receiving sensor and generates a match signal when they match. and a controlled device actuated by the coincidence signal of the comparing means. The timer means controls the control circuit 1 when the transistor 58 is turned on and an input signal is applied to the input capacitor his.
8 from standby mode to operating mode for a certain period of time, and automatically switches from operating mode to standby mode after this certain period of time has elapsed.

The code registration means has a function of storing code numbers received from the light receiving sensors 14 to 17 when the code registration switch 78 is in the on state. The code registration switch 78 is a switching means for switching the code registration means between a reading mode and a writing mode. The code registration means supplies a code signal to the comparison means in the read mode, and stores a new code signal received by the light receiving sensor in the write mode.

In the above configuration, the operation of the automotive optical electronic control device will be explained based on the operation sequence shown in FIG. 10.

At the start in Figure 10, the ignition key 12
When inserted into the ignition key cylinder 25 of the steering lock device W127 and rotated from the lock position to the start position, a mechanical lock mechanism (not shown) of the steering lock device 27 is unlocked. When the ignition key 12 is rotated to the start position, the trigger switch 55
is turned on, and steps 80 to 8 in FIG.
1. At this time, the transistor 58 is turned on, so the input voltage of the control circuit 18 is turned on. A trigger signal is supplied to the transistor 43, and the transistor 43 is turned on. Therefore, a reset signal is supplied to the reset terminal R of the control circuit 18 through the reset circuit 44, and the control circuit 18 is reset. When a trigger signal is applied to the input capo h I s, the timer means of the control circuit 18 is activated. Therefore, the control circuit 18 is switched from the standby mode to the operating mode for a certain period of time, and one infrared light emitting diode 22 of the light emitting device 11 is turned on.

At this time, since the ignition key 12 is rotated to the start position, the infrared light from the diode 22 is transmitted to the light guide member 13.
The light enters from the light receiving section 30 and is irradiated to the outside from the light emitting section 32. In this state, the infrared light emitted from the light emitting section 32 is received by the light receiving sensors 14 to 17. However, in step 82, when the light receiving sensors 14 to 17 do not receive infrared rays, it is determined that the ignition key 12 is a reversible ignition key. In the reversible ignition key, the light receiving section 30 is shifted by 180 degrees, so the other infrared light emitting diode 22 of the light emitting device 11 is turned on (step 83), and the control circuit 18 receives no further input from the light receiving sensors 14 to 17. Sometimes, in step 84, it is determined that the ignition key is of a different type.

You will be returned to the start.

When there is an input to any of the light receiving sensors 14 to 17 in step 82 or 84, in step 85 the control circuit 18 determines whether or not the code registration means is in the write mode. That is, when the code registration switch 78 is on or off, the control circuit 18 determines that it is in the write mode or the read mode.
is off and in the reading mode, the process proceeds to step 86, where the signals input from the light receiving sensors 14 to 17 are
It is determined whether the information is the same as the information stored in the OM77. If they are the same, proceed from step 86 to step 87, and control circuit 1
8 sends a detection signal, which is a coincidence signal, to the trigger circuit 19 from the output port o4 via amplifiers 74 and 75.

Thereafter, when a certain period of time has elapsed by the timer means, an output is generated from the output port O, turning on the transistor 69, turning off the transistor 43, and switching the control circuit 18 from the operating mode to the standby mode.

In step 85, when the code registration switch 78 is on and in the write mode, the signals received from the light receiving sensors 14 to 17 are stored in a RAM (random access memory) or a writable R
The information is stored in the OM 77, and thereafter, the newly stored information is compared with the signals received from the light receiving sensors 14 to 17.

In the above-described embodiment, if a light emitting diode that emits infrared light in an invisible region is used, it is impossible to determine which of the plurality of light emitting parts 32 is emitting light, so it can be said that the anti-theft effect is high in this respect. However, instead of infrared radiation in the invisible range, it is possible to use light-emitting diodes that generate ordinary visible light.

Further, although a starter inter-control relay is shown as a controlled device, the present invention is not limited to this.

It can be used as a switching element such as a transistor to control various devices such as an electrically operated lock device and a fuel supply control device.

Next, as shown in FIG. 1, the vehicle theft prevention device 100 according to the present invention uses a detection signal from the key detection means 10 provided in the steering lock device 27 and a starter switch 1.
a trigger circuit 19 that generates a trigger pulse when receiving a starter signal generated when 03 is turned on; a thyristor circuit 104 having a gate that receives the trigger pulse of the trigger circuit 19; It has a switching circuit 105, and a vehicle motion control device 106 to which power is supplied from a power source when the switching circuit 105 is on.

A conventional switch is used as the starter switch 103,
A rotating terminal 110 connected to the battery contacts a starter terminal 112 connected to an ignition terminal 111 connected to an ignition circuit 113. As illustrated, the trigger circuit 19 includes an input terminal 120 connected to the key detection means 10, an input terminal 121 connected to the starter terminal 112, an input terminal 122 connected to the battery, and an input terminal connected to the ignition terminal 111. It has a terminal 123.

Details of the trigger circuit 19 are shown in FIG. Input terminal 120
and 121 are connected to each input terminal of the AND gate 124. Input terminal 122 is connected to the emitter of transistor 125. Further, the input terminal 123 is connected to the base of the transistor 126 and the collector of the transistor 150 via a one-shot multivibrator 128 and a resistor 153. The collector of transistor 126 is resistor 1
27 to the base of the transistor 125;
The base of transistor 126 is connected to the collector of transistor 125 via resistor 151. The collector of transistor 125 is also connected to the input terminal of AND gate 124. The emitter of transistor 126 is grounded. The base of transistor 150 is connected to the output terminal of one-shot multivibrator 129 via resistor 152.

The output terminal of the AND gate 124 is connected to a one-shot multivibrator 129 that generates a trigger pulse. The pulse width of the trigger pulse generated by the one-shot multivibrator 129 ranges from several nanoseconds to 0.5 milliseconds. The output of the one-shot multivibrator 129 is connected to the base of a transistor 161 via a thyristor circuit 1.04 and a resistor 160. transistor 1
The collector of transistor 61 is connected to the base of transistor 126, and the emitter of transistor 160 is grounded.

Thyristor circuit 104 includes a first thyristor 130 and a second thyristor 131. first thyristor 13
The gates of thyristor 0 and second thyristor 131 are connected to one-shot multivibrator 129 via resistors 132 and 133, respectively. In addition, the first thyristor 130
and the cathodes of the second thyristor 131 are grounded.

The anode of the first thyristor 130 is connected to one end of a coil 135a of a relay 135 that constitutes the switching circuit 105. The other end of the coil 135a is the starter terminal 1
12. A movable piece 135b of the relay 135 is connected to the starter terminal 112 and the starter motor circuit 137. Further, the anode of the second thyristor 131 is connected via a resistor 138 to the base of a transistor 140 that constitutes a switching element. The emitter of transistor 140 is connected to ignition terminal 111, and the collector is connected to the base of transistor 141 forming shift lock control circuit 147. transistor 141
The collector of the transistor 141 is connected to one end of the shift lock solenoid 142, and the emitter of the transistor 141 is connected to ground.

The other end of the shift lock solenoid 142 is the fuse 136
connected to. Further, a brake switch 144 is connected between the collector of the transistor 141 and ground.

As shown in FIG. 3, a shift lock solenoid 142 of a shift lever lock device 148 constituted by a shift lock control circuit 147 operates a plunger 143 that can protrude into a movement path of a shift lever 146. Plunger 14
3 is pressed in the projecting direction by a spring 152.

In the above configuration, when a predetermined key is inserted into the steering lock device 27 and rotated, the key detection means 10 determines the predetermined key and applies a trigger signal to the input terminal 120 of the trigger circuit 19. Further, when the key is rotated to the "on position" of the steering lock device 27, the rotation terminal 110 comes into contact with the ignition terminal 111, and the battery voltage is applied to the ignition terminal 111. Therefore, a high voltage is applied to the ignition circuit 113, the input terminal 123 of the trigger circuit 19, and the emitter of the transistor 140. Further, when the key is rotated to the "start position", the rotation terminal 110 is connected to the starter terminal 112.

Therefore, one-shot multivibrator 129 generates a pulse, transistors 126 and 125 are turned on, trigger circuit 19 is switched from standby mode to operating mode, and AND gate 124 generates an output. The output of the AND gate 124 causes the one-shot multivibrator 129 to generate a trigger pulse. This trigger pulse is applied to each gate of the first thyristor 130 and the second thyristor 131. Therefore, the first thyristor 130 and the second thyristor 131 are turned on. Therefore, relay 135 is activated and starter motor circuit 137 is activated.

At the same time, the second thyristor 131 is turned on, so the transistor 140 is turned on. Therefore.

Transistor 141 is turned on, and key cylinder solenoid 142 and shift lock solenoid 142 are energized. Therefore, the plungers 145 and 151 move to the retracted position, allowing the ignition key cylinder 25 to be rotated and the shift lever 146 to be operated.

Since the trigger pulse of one-shot multivibrator 129 is applied to the base of transistor 150, transistor 150 is turned on. Therefore, transistors 126 and 125 are turned off, and trigger circuit 19 is automatically switched from operating mode to standby mode.

Actually, the trigger circuit 19 is constituted by a one-chip microcomputer and is switched to standby mode after generating a trigger pulse, so that malfunction of the thyristor circuit 104 due to malfunction of the trigger circuit 19 does not occur. Since the holding current of the second thyristor 131 is small, once the first thyristor 130 and the second thyristor 131 are turned on, they will not be turned off due to malfunction. Therefore, even if the battery voltage drops from 12V to about 5V or less when the starter motor circuit 137 is energized, the first thyristor 130 and the second thyristor 131 will not turn off.

Since the shift lever 146 can be operated after the starter motor circuit 137 is activated, it is possible to prevent an accident caused by a sudden start when starting the vehicle.

Further modifications are possible to the above-described embodiments of the invention. For example, key detection circuit 10 may be described in U.S. Pat.
The anti-theft device described in No. 099 may also be used.

11. υ Arc Length As described above, the anti-theft device for a vehicle of the present invention prevents the operation of the vehicle in the event of theft and reliably prevents accidents due to malfunction of the vehicle or malfunction of the electronic device, thereby making the vehicle safer. can be driven to.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a vehicle anti-theft device according to the present invention, Fig. 2 is an electric circuit diagram showing details of a trigger circuit used in this vehicle anti-theft device, and Fig. 3 is an installation diagram of a shift lever lock device. 4 is a partial sectional view showing the state, FIG. 4 is an electronic circuit diagram of the automotive optical electronic control device, FIG. 5 is a partial sectional view showing the state in which the ignition key is inserted into the steering lock device, and FIG. 6 is a partial sectional view showing the state. FIG. 7 is a sectional view taken along line A-A in FIG. 5, FIG. 8 is a perspective view of the ignition key, and FIG. A front view of the light guide member, FIG.
3 is a flowchart showing the operating order of the control circuit shown in the figure. 106. key detection means, 19. , trigger circuit. 276. Steering lock device, 100. . Vehicle anti-theft device, 103. , starter switch,
104. , thyristor circuit, 105. . switching circuit, 106. , vehicle vibration control device,
130. , first thyristor, 131. . second thyristor, 135. , relay, 135a0
．． Coil, diagram of the drawing (no change in content) Fig. 2 Fig. 3 Fig. - Fig. Tekuichi Kaminokuchi (method)

Claims (3)

[Claims] (1) A trigger circuit that generates a trigger pulse when it receives the detection signal of the key detection means provided in the steering lock device and the starter signal generated when the starter switch is turned on, and receives the trigger pulse of the trigger circuit. A theft prevention device for a vehicle, comprising: a thyristor circuit having a gate that is turned on; a switching circuit that is turned on when the thyristor circuit is conductive; and a vehicle drive control device that is supplied with power from a power source when the switching circuit is turned on. Device. (2) The vehicle anti-theft device according to claim 1, wherein the key detection means includes photoelectric conversion means for optically reading a key code provided on the key. (3) A trigger circuit that generates a trigger pulse when receiving the detection signal of the key detection means provided in the steering lock device and the starter signal generated when the starter switch is turned on, and receives the trigger pulse of the trigger circuit. a switching circuit that is turned on when the thyristor circuit is conductive; and a vehicle drive control device that is supplied with power from a power source when the switching circuit is turned on; and a second thyristor, the anode of the first thyristor is connected to the coil of the relay, one contact of the relay is connected to a power source, and the other contact of the relay is connected to an engine starter, The anode of the second thyristor is connected to the switching circuit, and when the switching circuit is on, power is supplied from the power supply through the ignition switch to the shift lock control circuit, and the shift lever lock device is unlocked by the output of the shift lock control circuit. A vehicle anti-theft device characterized by: