Method and apparatus for controlling supply of electric power to an indicator for indicating a state of the apparatus

A printer has an electric power supply controller which controls electric power supplied to an indicator indicating a state of the printer so as to prolong a driving time of the printer, which is driven by a battery. When the apparatus is set to an on-line state using an on-line key, electric power is initially supplied to an on-line LED, which indicates the apparatus is in the on-line state. Afterwards, when a predetermined time period has passed, the supply of electric power is cut off to the on-line LED, whereby the consumption of electric power supplied to the indicator can be minimized.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an apparatus such as a printer, and more 
specifically relates to an apparatus having an indicator such as a power 
light-emitting diode (LED) and an on-line LED indicating the operation 
mode, which is set by an operation key such as a power key and an on-line 
key, and relates to a method for supplying electric power to the 
indicator. 
2. Related Background Art 
A printer having an indicator such as an LED has hitherto been constructed 
such that the LED corresponding to and indicating each operation mode has 
been turned on continuously. For example, an on-line LED has been turned 
on continuously while the printer has been the in the on-line state, and a 
power LED has been turned on continuously while the electric power has 
been supplied to the printer. 
A problem with this type of printer is that power consumption used by the 
indicator unrelated to the recording operation is large and cannot be 
disregarded because, as stated above, an LED corresponding to each 
operation mode is turned on continuously while the printer is in the 
corresponding operation mode. 
Especially in a battery-powered printer, due to the power consumption of 
the indicator, the printer suffers from a problem in that a drivable time 
of the printer is significantly reduced. 
SUMMARY OF THE INVENTION 
This invention is designed to overcome the above problem in the background 
art and is based on a concept, which has not been recognized until now. 
This invention aims to solve the above-mentioned problem in the background 
art. It is accordingly an object of this invention to minimize power 
consumption of an indicator indicating a condition of the apparatus, in 
order to maximize driving time of the apparatus driven by a battery. 
Another object of this invention is to provide an apparatus including an 
indicator for indicating a predetermined state of the apparatus; an 
electric power supply device for supplying electric power to the indicator 
from a battery; a set-up device for setting up the apparatus in the 
predetermined state; and a controller for controlling the electric power 
supply device so that electric power is initially supplied to the 
indicator when the predetermined state of the apparatus is set up by the 
set-up device, and for controlling the electric power supply device so 
that the supply of electric power is stopped when a predetermined 
condition is met. 
A further object of the present invention is to incorporate the apparatus 
described above in a printing apparatus including a printing device for 
printing information from a host device on a printing medium. 
Still another object of this invention is to provide a method for supplying 
electric power to an indicator indicating a predetermined state of an 
apparatus, including the steps of providing the indicator, which is 
electrically driven by a battery; beginning supply of electric power from 
the battery to the indicator when the predetermined state of the apparatus 
is set up; and stopping supply of the electric power to the indicator when 
a predetermined condition is met.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Preferred embodiments of this invention will now be described in detail 
with reference to the accompanying drawings. 
In the printer shown in FIG. 1, reference numeral 1 indicates a CPU, which 
controls the printer, reference numeral 2 indicates an address decoder 
("00FFH" corresponds to an output level "L"), reference numeral 3 
indicates an OR gate, reference numeral 4 indicates a 4-bit data latch, 
reference numeral 5 indicates an LED switch or LED override switch which 
turns on and off an LED indicator, reference numerals 6, 7 and 8 indicate 
open-collector output NAND gates, reference numerals 9, 13, 14 and 15 
collectively indicate a pull-up resistance, reference numeral 10 indicates 
a power key, reference numeral 11 indicates an on-line key, reference 
numeral 12 indicates a font select key, and reference numerals 16, 17 and 
18 collectively indicate a current restriction resistance. 
Next, the operation of the printer according to the first embodiment will 
be described with reference to FIG. 1. 
In the construction shown in FIG. 1, after the user turns on power switch 
10 of the printer under the condition that LED switch 5 is turned off, an 
on-line switch is turned on. The power-on state and the on-line state of 
the apparatus are confirmed by the lighting of power LED 19 and on-line 
LED 20. Then, the lighting of the LEDs are turned off. The above operation 
will be explained in detail. 
When the user turns on the power key 10, which operates as a set-up means 
to set up the printer to a predetermined state, the CPU 1 starts to 
perform a power-on operation and outputs address "00FFH" to the address 
decoder 2 and outputs data "xxxxx001" from outlet ports D.sub.0 
.about.D.sub.7 to the 4 bit latch 4. At that time, CPU 1 outputs a clock 
signal from outlet port WR to the OR gate 3, and the clock signal from the 
outlet port WR is supplied to the 4 bit latch 4 through the OR gate 3, 
because output of the address decoder 2 becomes "L". The data output from 
the output ports D.sub.0 .about.D.sub.7 is latched by the 4 bit latch 4 in 
accordance with the clock signal sent through the OR gate 3, whereby the 
latch 4 sets the output Q.sub.0 to be "H" so as to turn on the LED 19. As 
a result, the power LED 19 is turned on. 
Next, when the user turns on the on-line key 11, the CPU 1 starts to 
perform an on-line operation and outputs address "00FFH" to the address 
decoder 2 and outputs data "xxxxx011" from outlet ports D.sub.0 
.about.D.sub.7 to the 4 bit latch 4. At that time, CPU 1 outputs a clock 
signal from outlet port WR to the OR gate 3, and the clock signal from the 
outlet port WR is supplied to the 4 bit latch 4 through the OR gate 3, 
because output of the address decoder 2 is "L". The data output from the 
output ports D.sub.0 .about.D.sub.7 is latched by the 4 bit latch 4 in 
accordance with the clock signal sent through the OR gate 3, whereby the 
latch 4 sets the output Q.sub.0 and Q.sub.1 to be "H" so as to turn on the 
LEDs 19 and 20. As a result, both the power LED 19 and the on-line LED 20 
are turned on. 
Next, when the user turns on the LED switch 5, a respective output level of 
open collector NAND gates 6, 7 and 8 becomes of high impedance. As a 
result, the power LED 19 and the on-line LED 20 are turned off. Similar 
operations can be carried out with a font LED 21, or other indicator LEDs. 
Thus, in accordance with this embodiment, an indicator can be selectively 
turned ON/OFF by the user, thereby reducing the electric power consumption 
of the printer in a case that the printer prints continuously in a same 
operation mode. 
Moreover, in the first embodiment, as shown in FIG. 1, reference numeral 40 
indicates a switch that is turned on when an alternating current (AC) 
power supply 41 is not connected to the printer, and is turned off when 
the AC power supply 41 is connected to the printer. In the above 
description, the printer is described using a battery as a power supply; 
however, when the AC power supply 41 is connected to the printer, it is 
not necessary to reduce the electric power consumption by cutting off the 
supply of electric power to the LEDs 19-21, and it would rather be 
preferable to keep the LEDs turned on in order to easily confirm the 
present operation mode visually. Accordingly, in the first embodiment, the 
switch 40 is provided and will be turned off when the AC power supply 41 
is connected to the printer. 
As the switch 40, a well-known switch capable of detecting the connection 
of the AC power supply to the printer mechanically or electrically can be 
used. When the switch 40 is turned off due to the connection of the AC 
power supply 41 to the printer, regardless of the turning-on of the LED 
switch 5, the respective output level of the open collector NAND gates 6, 
7 and 8 becomes of low-impedance state, thereby keeping the power LED 19 
and the on-line LED 20 turned on while the power key 10 and the on-line 
key 11 are turned on. Similar operations can be carried out with the font 
LED. 
Next, the second embodiment of this invention will be described in detail 
with reference to FIG. 2. 
FIG. 2 is a block diagram showing a circuit of the apparatus designed in 
accordance with the second embodiment of this invention as applied to a 
printer. 
In the drawing, those components common to FIG. 1 are referred to by the 
same reference numerals. 
In FIG. 2, reference numeral 1 indicates a CPU which controls the printer, 
reference numeral 2 indicates an address decoder ("00FFH" corresponds to 
an output level "L"), reference numeral 3 indicates an OR gate, reference 
numeral 4 indicates a 4 bit data latch, reference numeral 5 indicates an 
LED switch or LED override switch which turns on and off an LED indicator, 
reference numerals 6, 7 and 8 indicate open-collector output NAND gates, 
reference numerals 9, 13, 14 and 15 collectively indicate a pull-up 
resistance, reference numeral 10 indicates a power key, reference numeral 
11 indicates an on-line key, reference numeral 12 indicates a font select 
key, reference numerals 16, 17 and 18 collectively indicate a current 
restriction resistance of LED. 
An operation of the printer according to the second embodiment will be 
described hereinafter with reference to FIG. 2. 
In the construction shown in FIG. 2, after the user turns on the power 
switch of the printer under the condition that the LED switch 5 is turned 
ON, an on-line switch is turned on and the power-on state and the on-line 
state of the apparatus are confirmed by the lighting of the power LED 19 
and the on-line LED 20. Afterwards, these LEDs are turned off. 
The above operation will be explained in detail. 
When the user turns on the power key 10, which operates as a set-up means 
to set up the printer to a predetermined state, the CPU 1 starts to 
perform a power-on operation and outputs address "00FFH" to the address 
decoder 2 and outputs data "xxxxx001", from outlet ports D.sub.0 
.about.D.sub.7 to the 4 bit latch 4. At that time, CPU 1 outputs a clock 
signal from outlet port WR to the OR gate 3, and the clock signal from the 
outlet port WR is supplied to the 4 bit latch 4 through the OR gate 3, 
because output of the address decoder 2 becomes "L". The data output from 
the output ports D.sub.0 .about.D.sub.7 is latched by the 4 bit latch 4 in 
accordance with the clock signal sent through the OR gate 3, whereby the 
latch 4 sets the output Q.sub.0 to be "H" so as to turn on the LED 19. As 
a result, the power LED 19 is turned on. 
Next, when the user turns on the on-line key 11, the CPU 1 starts to 
perform an on-line operation and outputs address "00FFH" to the address 
decoder 2 and outputs data "xxxxx011" from outlet ports D.sub.0 
.about.D.sub.7 to the 4 bit latch 4. At that time, CPU 1 outputs a clock 
signal from outlet port WR to the OR gate 3, whereby the clock signal from 
the outlet port WR is supplied to the 4 bit latch 4 through the OR gate 3, 
because output of the address decoder 2 is "L". The data output from the 
output ports D.sub.0 .about.D.sub.7 is latched by the 4 bit latch 4 in 
accordance with the clock signal sent through the OR gate 3, whereby the 
latch 4 sets the output Q.sub.0 and Q.sub.1 to be "H" so as to turn on the 
LEDs 19 and 20. As a result, the power LED 19 and the on-line LED 20 are 
turned on. 
Next, when the user turns off the LED switch 5, as electric power from a 
battery power supply Vcc to the LED 19 and the LED 20 is cut off, the 
power LED 19 and the on-line LED 20 are turned off. Similar operations are 
carried out with the font LED 21. 
Thus, in accordance with the second embodiment, the indicators can be 
selectively turned ON/OFF by the user, thereby reducing the electric power 
consumed by the indicators and conserving electric power consumed by the 
printer when printing continuously in a same operation mode. 
The third embodiment of this invention will now be described in detail with 
reference to FIG. 3. 
FIG. 3 is a block diagram showing a circuit of the apparatus designed in 
accordance with the third embodiment of this invention as applied to a 
printer. 
In the drawing, those components common to FIG. 1 are referred to by the 
same reference numerals. 
In FIG. 3, reference numeral 1 indicates a CPU which controls the printer, 
reference numeral 2 indicates an address decoder ("00FFH" corresponds to 
an output level "L"), reference numerals 3 and 25 indicate OR gates, 
reference numeral 4 indicates a 4 bit data latch, reference numeral 50 
indicates a 4 bit counter, reference numerals 6, 7 and 8 indicate 
open-collector NAND gates, reference numerals 90 and 26 indicate 
inverters, reference numeral 10 indicates a power key, reference number 11 
indicates an on-line key, reference numeral 12 indicates a font select 
key, reference numerals 13, 14, 15 and 28 collectively indicate a pull-up 
resistance, reference numerals 16, 17 and 18 collectively indicate a 
current restriction resistance for LED, reference numeral 19 indicates a 
power LED and is turned on when the electric power is supplied to the 
printer, reference numeral 20 indicates an on-line LED and is turned on 
when the printer is in an on-line state, reference numeral 21 indicates a 
font LED and is turned off when an A font is selected and is turned on 
when a B font is selected, reference numeral 22 indicates an AND gate, and 
reference numeral 23 indicates a check key. 
An operation of the printer according to the third embodiment will be 
described hereinafter with reference to FIG. 3. 
A power-on operation carried out when the printer is in a power-off state, 
an on-line state and font A selected state (all LEDs are turned off) will 
be described. 
When the user turns on the power key 10 while in the power-off state, a 
level of a port input Po is changed from H to L. The CPU 1 detects this 
change and carries out the power-on operation of the printer, and writes 
the data "xxxxx001" in an address "00FFH" Then, a level of the output Qo 
of the 4 bit latch 4 is changed from "L" to "H", and the 4 bit counter 50 
is cleared. Then, Co level is changed from "H" to "L", and an output level 
of the open collector NAND gate 6 is changed from high impedance to "L". 
As a result, the power LED 19 is turned on. Next, the 4 bit counter 50 
counts input clock CLK and when the count value becomes "FH", Co level is 
changed from "L" to "H", the output level of the inverter 90 becomes "L", 
and the output level of the open collector AND gate 6 is changed from "L" 
to "high impedance". Then, the power LED is turned off. 
When the user uses the on-line key 11 and font key 12, operation sequences 
similar to the above-mentioned sequence are carried out. As a result, an 
on-line LED is turned on for a predetermined time period when the printer 
state is changed from an off-line state to an on-line state, and a font 
LED is turned on for a predetermined time period when the font is changed 
from A to B. 
Further, when the user wants to confirm the state of the printer, by 
turning on the check key 23, the input level of the inverter 26 becomes 
"L" for as long as the check key 23 is activated. Then, the output level 
of OR gate 25 forcibly becomes "H", and an LED corresponding to each 
operation mode is turned on. 
Thus, in accordance with this embodiment, when the user turns on a key to 
set up the desired operation, or even after the LED corresponding to each 
operation is turned off, when the user turns on the check key, the LED 
corresponding to each operation mode can be turned on, thereby reducing 
the electric power consumed by the LED without affecting the ease with 
which the user can visually confirm the LEDs. 
Further, in this embodiment, by providing a switch means that sets up an 
input level of the inverter 26 to "L" while the AC power supply is 
connected to the printer, the LED corresponding to each operation mode can 
be turned on continuously while the key corresponding to each operation 
mode is turned on. Accordingly, the user can continuously confirm the LEDs 
visually. 
The fourth embodiment of this invention will now be described in detail 
with reference to FIG. 4. 
FIG. 4 is a block diagram showing a circuit of the apparatus designed in 
accordance with the fourth embodiment of this invention as applied to a 
printer. 
In the drawing, those components common to the above-mentioned embodiments 
are referred to by the same reference numerals. 
In FIG. 4, reference numeral 1 indicates a CPU, reference numeral 2 
indicates an address decoder ("00FFH" corresponds to an output level "L"), 
reference numeral 3 indicates an OR gate, reference numeral 4 indicates a 
4 bit data latch, reference numeral 125 indicates a NAND gate having three 
inputs ports, reference numerals 6, 7 and 8 each indicate a NAND gate, 
reference numeral 10 indicates a power key, reference numeral 11 indicates 
an on-line key, reference numeral 12 indicates a font select key, 
reference numeral 120 indicates an OR gate, reference numerals 13, 14, 15 
and 28 collectively indicate a pull-up resistance, reference numerals 16, 
17 and 18 collectively indicate a current restriction resistance for LED, 
reference numeral 19 indicates a power LED and is turned on when the 
electric power is supplied to the printer, reference numeral 20 indicates 
an on-line LED and is turned on when the printer is in an on-line state, 
reference numeral 21 indicates a font LED and is turned off when the A 
font is selected and is turned on when the B font is selected, reference 
numeral 22 indicates an AND gate, reference numeral 23 indicates a check 
key, and reference numeral 25 indicates an inverter. 
Next, an operation of the printer according to the fourth embodiment will 
be described with reference to FIG. 4. 
A power-on operation carried out while the printer is in the power-off 
state, an on-line state and font A selected state (all LEDs are turned 
off) will be described. 
When the user turns on the power key 10 under the above-mentioned state, an 
input port Po level is changed from H to L. The CPU 1 detects this change 
and starts to perform a power-on operation of the printer by outputting 
address "00FFH" to the address decoder 2 and outputting data "xxxxx001" 
from outlet ports D.sub.0 .about.D.sub.7 to the 4 bit latch 4. At that 
time, CPU 1 outputs a clock signal from outlet port WR to the OR gate 3, 
and the clock signal from the outlet port WR is supplied to the 4 bit 
latch 4 through the OR gate 3, because output of the address decoder 2 
becomes "L". The data output from the output ports D.sub.0 .about.D.sub.7 
is latched by the 4 bit latch 4 in accordance with the clock signal sent 
through the OR gate 3. Then, a level of the output Q.sub.0 of the 4 bit 
latch 4 becomes "H", an output level of the AND gate 22 becomes "H" while 
the user is activating the power key 10, and the output level of the open 
collector NAND gate 6 becomes "L". As a result, the power LED 19 is turned 
on. 
Next, when the user stops actuating the power key 10, the power key 10 is 
turned off and output level of the AND gate 22 becomes "L", and the output 
level of the open collector NAND gate 6 becomes of high impedance 
condition (H). As a result, the power LED 19 is turned off. 
When using the on-line key 11 or the font select key 12, operation 
sequences similar to the above-mentioned sequence is carried out. 
Accordingly, when the operation mode is changed from an off-line mode to 
an on-line mode by using the on-line key 11, the on-line LED is turned on 
while the user is activating the on-line key 11, and when the font is 
changed from the A font to the B font by using the font select key 12, the 
font LED is turned on while the user is activating the font select key 12. 
Further, when the user wants to know the state of the printer, by turning 
on the check key 23, an output level of the inverter 25 becomes "H", and 
an output level of the OR gate 120 forcibly becomes "H". As a result, the 
LED corresponding to each operation turns on. 
Thus, in accordance with this embodiment, the power consumed by the LED can 
be reduced without affecting the ease with which the user can visually 
confirm the LEDs. 
Next, the fifth embodiment of this invention will now be described in 
detail with reference to FIG. 5. 
FIG. 5 is a block diagram showing a circuit of the apparatus designed in 
accordance with the fifth embodiment of this invention as applied to a 
printer. 
In the drawing, those components common to the above-mentioned embodiments 
are referred to by the same reference numerals. 
In FIG. 5, reference numeral 1 indicates a CPU which controls the printer, 
reference numeral 2 indicates an address decoder ("00FF" corresponds to an 
output level "L"), reference numeral 3 indicates an OR gate, reference 
numeral 4 indicates a 4 bit data latch, reference numeral 35 indicates a 
check key which is used by the user to turn ON/OFF an indicator at will, 
reference numerals 36, 37 and 38 indicate open collector output inverters, 
reference numerals 13, 14, 15 and 39 collectively indicate a pull-up 
resistance, reference numeral 10 indicates a power key, reference numeral 
11 indicates an on-line key, reference numeral 12 indicates a font select 
key, reference numerals 16, 17 and 18 collectively indicate a current 
restriction resistance, reference numerals 32 and 33 each indicate a 
transistor organizing a complementary constitution. 
An operation of the printer according to the fifth embodiment will be 
described hereinafter with reference to FIG. 5. 
After the user turns on the power key while the check key 35 is turned off, 
when the user turns on the on-line key, the on-line LED is turned on and 
is afterward turned off. Then, when the user turns on the check key to 
check the present mode, each LED is turned on again. 
The above-mentioned outline will be described in detail. When the user 
turns on the power key 10, which operates as a set-up means to set up the 
printer to a predetermined state, the CPU 1 starts to perform a power-on 
operation and sets a level of P4 to "H" to turn on transistors 32 and 33 
and outputs address "00FFH" to the address decoder 2 and outputs data 
"xxxxx00" from outlet ports D.sub.0 .about.D.sub.7 to the 4 bit latch 4. 
At that time, CPU 1 outputs a clock signal from outlet port WR to the OR 
gate 3. The clock signal from the outlet port WR is supplied to the 4 bit 
latch 4 through the OR gate 3, because output of the address decoder 2 
becomes "L". The data output from the output ports D.sub.0 .about.D.sub.7 
is latched the 4 bit latch 4 in accordance with the clock signal sent 
through the OR gate 3, whereby the latch 4 sets the output Q.sub.0 to be 
"H" so as to turn on the LED 19. When the power LED 19 is turned on, the 
CPU 1 starts an internal timer and when the internal timer counts up to a 
predetermined value, an internal interrupt is generated in the CPU 1, and 
CPU 1 judges that a predetermined time period has passed, and changes a 
level of P4 to "L" to turn off transistors 32 and 33, and the power LED 19 
is turned off. 
Next, when the user turns on an on-line key 11, the CPU 1 starts to perform 
an on-line operation, and at the same time, the CPU 1 sets a level of P4 
to "H" to turn on transistors 32 and 33 and outputs address "00FFH" to the 
address decoder 2 and outputs data "xxxxx011" from outlet ports D.sub.0 
.about.D.sub.7 to the 4 bit latch 4. At that time, CPU 1 outputs a clock 
signal from outlet port WE to the OR gate 3. The clock signal from the 
outlet port WR is supplied to the 4 bit latch 4 through the OR gate 3, 
because output of the address decoder 2 is "L". The data output from the 
output ports D.sub.0 .about.D.sub.7 is latched by the 4 bit latch 4 in 
accordance with the clock signal sent through the OR gate 3, whereby the 
latch 4 sets the output Q.sub.0 and Q.sub.1 to be "H" so as to turn on the 
LEDs 19 and 20. Then, the power LED 19 and the on-line LED 20 are turned 
on and the CPU 1 starts an internal timer. Afterwards, when the timer 
counts up the predetermined value, an internal interrupt is generated in 
the CPU 1 and the CPU 1 judges that a predetermined time period has passed 
after the LEDs have turned on, and the CPU 1 changes a level of P4 to "L" 
to turn off transistors 32 and 33. Then, the power LED 19 and the on-line 
LED 20 are turned off. 
When the user turns on the check key 35 to confirm the present mode of the 
printer, the CPU 1 changes a level of P4 to "H" to turn on transistors 32 
and 33 during the period that the check key 35 is turned on, and the power 
LED 19 and the on-line LED 20 are turned on due to an output ("0011") of 
the 4 bit latch. Afterwards, when the user turns off the check key 35, the 
CPU 1 changes a level of P4 to "L" to turn off transistors 32 and 33. 
Then, the power LED 19 and the on-line LED 20 are turned off. 
If an error occurs in the printer for some reason, the CPU 1 changes a 
level of P4 to "H" and writes data "xxxxx001" and "xxxxx000" in an address 
"00FFH" alternately. Then the power LED is repeatedly turned on and off. 
That is, when there occurs no error in the printer, at first, an LED 
corresponding to each operation mode is turned on, and after the 
predetermined time period has passed, all LEDs are turned off. However, 
when an error occurs in the printer, the power LED is flashed on and off, 
whereby, compared with that a usual error LED, which is continuously 
turned on, visual recognition of an error can be improved. 
Next, other features of the fifth embodiment will be described. 
In recent years, a printer is often connected to LAN (local area network) 
such as APPLE TALK (trademark) or NETWARE (trademark), and printing is 
often carried out under the condition that the printer is connected to 
LAN. Printing is carried out using a printer placed near the host, e.g., a 
personal computer or a work station. Moreover, printing is often carried 
out using a printer placed in the LAN area which is apart from the host by 
10.about.16 feet, for example. 
In the latter situation, when an error occurs in the printer, for example, 
a paper for printing is exhausted, since the printer is placed apart from 
the host by 10.about.16 feet and indication letters identifying each LED 
on a panel of the printer are difficult to read, so it is difficult to 
discriminate which LED is lit, and difficult to confirm whether the LED is 
turned on due to an occurrence of some error or is turned on merely to 
indicate an operation mode. 
According to the fifth embodiment, however, this problem can be solved. The 
reason will be described in the actual printing procedure. When the user 
uses the printer placed apart from the host by 10.about.16 feet, the user 
turns on a power switch on the spot, whereby the user can confirm the 
operation mode, etc. on the spot. After the user confirms that the printer 
is in good order, the user operates the printer from the place where the 
host is placed, which is apart from the printer by 10.about.16 feet If the 
LED is turned off after the predetermined time period has passed, the user 
can readily realize that the printer is in a normal condition and is 
awaiting orders normally. 
Then, if no trouble occurs while the user is operating the printer by means 
of the LAN from the host, the LEDs are not turned on and off, but rather 
maintain the turned-off state, and the user can realize that the printer 
is in a normal condition. The user, therefore, confidently completes the 
printing operation. 
On the other hand, when some trouble occurs in the printer, for example, a 
paper for printing is exhausted, any LED is turned on and off, whereby the 
user can be alerted of the occurrence of the trouble quickly, even if the 
user is in the area where the host is placed apart from the printer by 
10.about.16 feet. 
Thus, in accordance with the fifth embodiment, a printer, having not only a 
battery power saving effect but also high efficiency to visually inform 
the user of an error, can be provided. 
The individual components shown in outline or designated by blocks in the 
drawings are all well-known in the electronics and image recording arts 
and their specific construction and operation are not critical to the 
operation or best mode for carrying out the invention. 
While the present invention has been described with respect to what is 
presently considered to be the preferred embodiments, it is to be 
understood that the invention is not limited to the disclosed embodiments. 
To the contrary, the invention is intended to cover various modifications 
and equivalent arrangements included within the spirit and scope of the 
appended claims. The scope of the following claims is to be accorded the 
broadest interpretation so as to encompass all such modifications and 
equivalent structures and functions.