Abstract:
A tuner block in which a modulator and an IF/demodulator circuit are integrally formed. The tuner block has a casing for accommodating a tuner, the IF/demodulator circuit and the modulator, and sixteen pins consecutively disposed at an outside of the casing. A number of the pins is reduced as compared with a conventional tuner block by supplying an electrical power to the modulator and the tuner through a common pin, dispensing with pins carrying unnecessary signals and pins which carry no signal and rearranging other pins. Potential for noise and interference between signals is reduced by maximizing displacements of connector pins which carry signals which are likely to interact. A switching arrangement provides for utilizing either a conventional tuner block or a tuner block according to the present invention on a circuit board.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of and claims the benefit of U.S. patent application Ser. No. 10/045,043 filed on Jan. 15, 2002, in the U.S. Patent and Trademark Office, the disclosure of which is incorporated by reference. U.S. Pat. No. 6,947,722 issued from U.S. patent application Ser. No.: 10/045,043 on Sep. 20, 2005. This application also claims the benefit of Korean Application No. 2001-62462 filed Oct. 10, 2001, in the Korean Patent Office, the disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a tuner block for a broadcasting signal receiving apparatus such as a VCR, and more particularly, to a tuner block having a modulator, a tuner and IF/demodulator circuit which are built integrally in a casing. 
   2. Description of the Related Art 
   As shown in  FIG. 1 , a broadcasting signal receiving apparatus such as a VCR comprises an A/V block  10  for processing a video signal and an audio signal, a deck  20  for recording/reproducing the video signal and the audio signal on/from a recording medium such as a magnetic tape, a tuner block  50  for demodulating the video signal and the audio signal from the broadcasting signal transmitted through an antenna  60 , and a CPU  30  which controls the broadcasting signal receiving apparatus. The tuner block  50  has a tuner  53  for tuning the broadcasting signal, an IF/demodulator circuit  55  for demodulating the tuned broadcasting signal, and a modulator  51  for modulating the video signal and the audio signal into an RF signal for a TV  70 . 
   Generally, the modulator  51 , the tuner  53 , and the IF/demodulator circuit  55  are integrally built in a casing, and such a device is called as an integral-type of tuner block. The tuner block  50  is mounted on a printed circuit board in the VCR. The tuner block  50  is connected with other devices such as the A/V block  10  and the CPU  30  mounted on the printed circuit board. 
     FIG. 2  is a view showing an appearance of the conventional tuner block  50  that has the modulator  51 , the tuner  53  and the IF/demodulator circuit  55  integrally formed therein.  FIG. 3  is a view showing a layout of an arrangement of a plurality of pins of the tuner block  50  shown in  FIG. 2 . 
   As shown in  FIG. 2 , the tuner block  50  has a casing  50   c  for embracing the modulator  51 , the tuner  53 , and the IF/demodulator circuit  55 , and an antenna input terminal  50   a  and an antenna output terminal  50   b  disposed at an outside of the casing  50   c . The antenna input terminal  50   a  is connected with the antenna  60 , and the antenna output terminal  50   b  is connected with the TV  70 . A length of the casing  50   c  is standardized as 85 mm considering the arrangement of the plurality of pins installed on the casing  50   c.    
   As shown in  FIG. 3 , twenty-two pins are installed in the casing  50   c . The 22 pins consist of five pins (pin  1  through pin  5 ) corresponding to the modulator  51 , twelve pins (pin  6  through pin  16  and pin  21 ) corresponding to the tuner  53 , and five pins (pin  17  through pin  20  and pin  22 ) corresponding to the IF/demodulator circuit  55 . 
   The five pins allocated to the modulator  51  comprise pin  1  and pin  5  (AUDIO IN, VIDEO IN) to input the audio signal and the video signal, respectively, pin  2  (CH/SW) to input a channel selection signal, pin  3  (MB (5V)) to supply electrical power needed for the modulator  51 , and pin  4  (CONTROL) to input a control signal for a mode conversion between a TV mode and a VCR mode. 
   The twelve pins allocated to the tuner  53  comprise pin  6  (RF AGC) to control a gain of an input signal, pin  9  and pin  10  (SCL, SDA) connected with control buses to communicate with the CPU  30  through I 2 C communication, pin  13  (X-TAL IN) to input a clock signal, etc. Among the twelve pins allocated to the tuner  53 , pin  7 , pin  11 , and pin  15  are not used. 
   The five pins allocated to the IF/demodulator circuit  55  comprise pin  19  and pin  22  (AUDIO OUT, VIDEO OUT) to output an audio signal and a video signal, respectively, pin  20  (SIF OUT) to output a sound sub-carrier, etc. Among these pins allocated to the IF/demodulator circuit  55 , pin  17  and pin  18  are not used. 
   Such an arrangement of the pins is determined considering the position of three ICs (Integrated Circuits) corresponding to the modulator  51 , the tuner  53 , and the IF/demodulator circuit  55  disposed in the casing  50   c . In other words, the ICs, which correspond to the modulator  51 , the tuner  53 , and IF/demodulator circuit  55 , are consecutively disposed from an adjacent place to the antenna input terminal  50   a  and the antenna output terminal  50   b  in the casing  50   c . Considering the position of the ICs, the pins used by the modulator  51  are disposed near to the antenna input terminal  50   a  and the antenna output terminal  50   b , the pins used by the tuner  53  are disposed at a next position, and the pins used by the IF/demodulator circuit  55  are disposed at a farthest place from the antenna input terminal  50   a  and the antenna output terminal  50   b.    
   Moreover, the arrangement of the pins is determined considering a necessity of maintaining a distance between pins which conduct signals that may cause interference if the pins are disposed closely to each other. For example, where the video output pin and the audio output pin are closely disposed, the video output signal causes interference to the audio output signal, thus noise is added to the audio signal. Therefore, the video output pin and the audio output pin are disposed respectively at pin  22  and pin  19  so as to be spaced by more than a predetermined distance. 
   However, a size of the conventional tuner block  50  becomes unnecessarily large since more pins are disposed than the number of pins actually needed for the broadcasting signal receiving apparatus. In other words, as described above, pins  7 ,  11 ,  15 ,  17 , and  18  are not necessary since these pins are not used. Yet, the conventional tuner block  50  has the pins that are not used, thus the size of the tuner block  50  becomes unnecessarily large. Thus, it is difficult to realize a compact broadcasting signal receiving apparatus because of the unnecessarily large tuner block  50 . 
   Recently, an IC having an integrally formed tuner and IF/demodulator circuit has been developed. Therefore, a tuner block having simpler construction may be manufactured by installing two ICs (a modulator IC and the integrated tuner and IF/demodulator circuit IC) in the casing. Accordingly, a small-sized tuner block may be created. 
   However, the arrangement of the pins according to the position of the modulator IC and the integrated tuner and the IF/demodulator circuit IC in the casing  50   c , and signal interference problem between the pins in accordance with the position of the pins should be considered, even in the case of manufacturing the tuner block by adopting the IC in which the tuner and the IF/demodulator circuit are integrally formed. Therefore, to move some of the used pins to the position of the unused pins (pin  7 ,  11 ,  15 ,  17 ,  18 ) to reduce the number of the pins complicates construction of a circuit that connects the modulator IC and the integrated tuner and IF/demodulator circuit IC in the casing  50   c  and increases a probability that noise caused by the signal interference will be generated. 
   SUMMARY OF THE INVENTION 
   The present invention has been made to overcome the above-mentioned problems of the related art. Accordingly, it is a first object of the present invention to provide a small sized tuner block comprising an integrally formed modulator and IF/demodulator circuit, wherein some pins of the small sized tuner block have the same function as pins in a conventional tuner block. 
   A second object of the present invention is to provide a tuner block comprising an integrally formed modulator and IF/demodulator circuit, which realizes a compact casing and simplifies circuit construction in the casing, by determining positions of the pins in consideration of a position of a modulator IC and an integrated tuner and IF/demodulator circuit IC disposed in the casing. 
   A third object of the present invention is to provide a tuner block comprising an integrally formed modulator and IF/demodulator circuit, which creates a compact casing and minimizes the generation of a noise and interference between signals due to the compact casing. 
   Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention. 
   To accomplish the first object and other objects of the invention, the present invention comprises: a tuner which tunes a broadcast signal, an IF/demodulator circuit which demodulates the broadcast signal, a modulator which modulates a video signal and an audio signal into an RF signal, a casing which accommodates the tuner, the IF/demodulator circuit and the modulator, and a plurality of pins, disposed consecutively on an outside of the casing, which input and output signals and a voltage to operate the tuner, the IF/demodulator circuit and the modulator. 
   Here, one of the plurality of pins is a power supply pin through which an electrical power is supplied from an outside power supply. The tuner and the modulator are commonly connected to the power supply pin at an inside of the casing, whereby the tuner and the modulator are supplied with the electrical power required for a normal operation thereof through the power supply pin. Since the modulator and the tuner are supplied from a common pin, the number of the pins is reduced and a tuner block may be manufactured which is smaller in size compared with the conventional tuner block. 
   As shown in  FIG. 5 , a total number of pins is sixteen. Among the sixteen pins, a first pin through a fifth pin are used by the modulator, a sixth pin through an eleventh pin and a fourteenth pin are used by the tuner, and a twelfth, a thirteenth pin and a sixteenth pin are used by the IF/demodulator circuit. In addition, a fifteenth pin is a reserved pin, which is not used. The reserved pin may be removed, reducing the total number of the pins to fifteen. 
   The third pin is a power supply pin, and the seventh pin is a clock input pin to input a clock signal for use in the modulator and the tuner. 
   The tuner block to accomplish the second and the third object comprises: an audio output pin which outputs an audio signal demodulated by the IF/demodulator circuit; a video output pin distanced from the audio output pin at least by an interval as much as four of the pins, a video output pin which outputs the video signal demodulated by the IF/demodulator circuit; an SIF output pin disposed adjacent the audio output pin, the SIF output pin outputting a sound sub-carrier; and a clock input pin distanced from the SIF output pin at least by another interval as much as six of the pins, the clock input pin inputting a clock signal for use in the modulator and the tuner. 
   Preferably, the SIF output pin is disposed between the audio output pin and the video output pin. Accordingly, the SIF pin and the clock input pin are disposed for more than the distance of six pins as described above. 
   A TU-V pin which outputs a reference voltage used for a local oscillation of a frequency required by a selected channel and a reserved pin, which is not used, are disposed between the SIF output pin and the video output pin. 
   The total number of pins is sixteen. The audio output pin, the SIF output pin, the TU-V pin, the reserved pin and the video output pin are respectively a twelfth pin through a sixteenth pin among the sixteen pins, and the clock input pin is a seventh pin. 
   The first pin through the fifth pin are used by the modulator. The pins are respectively: an audio input pin which inputs the audio signal transmitted from an audio/video block; a channel selection pin which inputs a channel selection signal which selects an output channel of the modulator; a power supply pin which supplies an electrical power to the modulator and the tuner; a control pin which inputs a control signal for a mode conversion between a TV mode and a VCR mode; and a video input pin which inputs the video signal transmitted from the audio/video block. 
   A sixth pin and an eighth pin through an eleventh pin are used by the tuner. The pins are respectively: an automatic gain control pin which controls a gain of the broadcasting signal tuned by the tuner; an AS pin which inputs a signal which selects the tuner to be controlled; an SCL pin which inputs another clock signal used for a communication with respect to a CPU, an SDA pin which inputs a command transmitted from the CPU; and an AFT pin which outputs another reference voltage provided to the CPU, the another reference voltage being used for an automatic fine tuning. 
   Accordingly, the pins are disposed to correspond to the position of the modulator IC and the integrated tuner and IF/demodulator IC installed in the casing. Therefore, the compact tuner block may be realized and at the same time, a circuit construction in the casing is simplified. Furthermore, interference between the signals and the noise is minimized in the compact tuner block. 
   According to the present invention, the number of the pins is reduced to sixteen and a small-sized tuner block is realized. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned objects and the feature of the present invention will be more apparent by describing an embodiment of the present invention by referring to the appended drawings, in which: 
       FIG. 1  is a schematic block diagram showing a conventional broadcasting signal receiving apparatus; 
       FIG. 2  is a view showing an appearance of the tuner block having an integrated modulator and an IF/demodulator circuit of  FIG. 1 ; 
       FIG. 3  is a view showing a layout of pins of the tuner block of  FIG. 2 ; 
       FIG. 4  is a view showing an appearance of the tuner block having an integrated modulator and an IF/demodulator circuit according to the present invention; 
       FIG. 5  is a view showing a layout of pins of the tuner block in  FIG. 4 ; and 
       FIG. 6A  is a view showing a switching status of a printed circuit board adapted to accommodate either the tuner block of  FIG. 2  or the tuner block of  FIG. 4  and showing a switching status for operation of the tuner block of  FIG. 2 . 
       FIG. 6B  is a view showing a switching status of the printed circuit board shown in  FIG. 6A  and showing a switching status for operation of the tuner block of  FIG. 5 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     FIG. 4  is a view showing the appearance of a tuner block comprising a modulator and an IF/demodulator circuit according to the present invention. The tuner block  150  comprises a modulator, a tuner, an IF/demodulator circuit and a casing  150   c  which accommodates the modulator, the tuner, and the IF/demodulator circuit. An antenna input terminal  150   a  and an antenna output terminal  150   b  are installed at an outside of the casing  150   c . A modulator IC is disposed at an adjacent position to the antenna input terminal  150   a  and the antenna output terminal  150   b  in the casing  150   c . An integrated tuner and IF/demodulator circuit IC is disposed at a distant place from the position of the modulator IC. 
   Sixteen pins are disposed at a side of the casing  150   c . The physical construction of each of the sixteen pins, such as size and shape of a pin, are the same as a pin of the conventional tuner block  50  in  FIG. 2  and a distance between pins is the same as a distance between pins of the conventional tuner block  50 . The casing  150   c  is formed to have a length of 60 to 65 mm, which is smaller than the conventional tuner block  50 , since the number of the pins is reduced compared to the conventional tuner block  50 . Preferably, the tuner block  150  according to the present invention has the length of 65 mm as shown in  FIG. 4 . 
     FIG. 5  is a view showing a layout of pins used in the tuner block  150  of  FIG. 4 . Pin  1  and pin  5  (AUDIO IN, VIDEO IN) input an audio signal and a video signal, respectively, transmitted from an audio/video block. Pin  2  (CH/SW) inputs a channel selection signal (to select one channel between channel  3  and channel  4 ) which selects an output channel of the modulator. Pin  4  inputs a control signal which converts between a TV mode and a VCR mode. 
   Pin  3  (+B (TU/MD) supplies electrical power to the modulator and the tuner. Thus, pin  1  through pin  5  are all used by the modulator. Among these pins, pin  3  is used for supplying the electrical power not only to the modulator but also to the tuner. To allow pin  3  to supply the electrical power to both the modulator and the tuner, electrical power supply reeds of the modulator IC and the integrated tuner and IF/demodulator circuit IC are commonly connected with pin  3  in the casing  150   c.    
   Pin  6  (RF AGC) inputs a bias voltage to control a gain of the broadcasting signal tuned by the tuner. Pin  7  (X-TAL IN) inputs a clock signal for use in the modulator and the tuner. Pin  8  (AS) inputs a signal for appointing an address of a tuner to be controlled where there is a plurality of tuners. Pin  9  (SCL) inputs another clock signal used for communication with respect to a CPU through an I 2 C communication. Pin  10  (SDA) inputs a command transmitted from the CPU through the I 2 C communication. Pin  11  (AFT) outputs a reference voltage, which is provided to the CPU for an automatic fine tuning. Pin  12  (AUDIO OUT) outputs the audio signal. Pin  13  (SIF OUT) outputs a sound sub-carrier (4.5 MHz in the case of an NTSC method). Pin  14  (TU-V) outputs another reference voltage used for local oscillation of a frequency required by a selected channel. Pin  15  is a reserved pin, which is not used. Pin  16  (VIDEO OUT) outputs the video signal. 
   According to the above construction of the pins, pins  1  through  5  are used by the modulator, and pins  6  through  11  and  14  are used by the tuner. Pins  12 ,  13  and  16  are used by the IF/demodulator circuit  55 , and pin  15  is not used. Pin  3  and pin  7  are used by both of the modulator and the tuner. 
   According to the arrangement of the pins as described above, among pins allocated to the tuner  53  and the IF/demodulator circuit  55  in the conventional tuner block  50  of  FIG. 3 , six pins (pin  17  through  22 ) which are used in the conventional tuner block  50 , are eliminated and functions of the eliminated pins are included among the sixteen pins of the tuner block  150 . Actually, the IF/demodulator circuit  55  of the conventional tuner block  50  uses only four pins (pins  19  through  22 ), thus among pins (pin  1  through  16 ) allocated to the modulator  51  and the tuner  53  of the conventional tuner block  50 , five pins are required to be reassigned to provide the interconnections previously provided by pins  19  through  22 . Electrical power supply pin (pin  3 ) for the modulator and the electrical power supply pin (pin  12 ) for the tuner in the conventional tuner block  50  are integrated into pin  3  in the tuner block  150 . Considering that the IF OUT pin (pin  16 ) in the conventional tuner block  50  is only used for testing, the IF OUT function has been removed and the VIDEO OUT function has been assigned to pin  16 . Pin  15  is a reserved pin in both the conventional tuner block  50  and the tuner block  150 . Where the reserved pin is also removed, the total number of the pins becomes fifteen. 
   In the tuner block  150  according to the present invention, the arrangement of several pins is different from the conventional tuner block  50  as will be described in great detail below. 
   The arrangement of pins  1  through  6 , pins  8  through  10 , and pin  14  is the same as the arrangement of pins  1  through  6 , pins  8  through  10 , and pin  14  of the conventional tuner block  50 . However, in the conventional tuner block  50 , pin  3  is used for supplying the electrical power to the modulator, but in the tuner block  150  according to the present invention, pin  3  is used for supplying the electrical power to both the modulator and the tuner. 
   The clock input pin (X-TAL IN), which was pin  13  in the conventional tuner block  50 , has been moved to pin  7 , which was not used in the conventional tuner block  50 . 
   The audio output pin (AUDIO OUT), which was pin  19  in the conventional tuner block  50 , has been moved to pin  12 , which was used in the conventional tuner block  50  as power input for the tuner. Pin  12  of the conventional tuner block  50 , as described above, has been integrated with pin  3 . The video output (VIDEO OUT), which was pin  22  in the conventional tuner block  50 , has been moved to pin  16  which was used as IF OUT in the conventional tuner block  50 . As described above, in the tuner block  150  of the present invention, the IF OUT function has been removed. 
   The sub sound carrier signal (SIF OUT), which was pin  20  in the conventional tuner block  50 , has been moved to pin  13 , which was used as the clock input signal (X-TAL IN) in the conventional tuner block  50 . The AFT signal, which was pin  21  in the conventional tuner block  50 , has been moved to pin  11 , which was not used in the conventional tuner block  50 . 
   According to the above construction, the electrical power needed for the tuner and the modulator is supplied through pin  3 , some of the previously reserved pins are used, the IF OUT function is eliminated, the number of the pins is reduced from  22  to  16 , and one reserved pin is retained. 
   Since the audio output pin (AUDIO OUT) and the video output pin (VIDEO OUT) are respectively disposed at pin  12  and pin  16 , the pins  12  and  16  are disposed to have an interval of four pins. Where the video output and the audio output are output from pins adjacent to each other, the video output becomes a noise source to the audio output. According to the present invention, the distance between the video output pin (VIDEO OUT) and the audio output pin (AUDIO OUT) becomes farther by one pin interval in comparison with that in the conventional tuner block  50 . Therefore, the influence of the video output signal on the audio output signal becomes less, and the audio signal will have a better quality. 
   In addition, according to the present invention, the audio output pin (AUDIO OUT) and the SIF OUT pin are adjacently disposed. The signals output from the audio output pin (AUDIO OUT) and the SIF OUT pin are input to an A/V block. Generally, there are two types of the AN block: one is a mono model, and the other is a hi-fi model having a hi-fi (Hi-Fi: High Fidelity) IC. The hi-fi IC generates a final audio signal after a predetermined signal processing in regard to the output signal of the SIF OUT pin, and passes through the output signal of the AUDIO OUT pin. Therefore, in the case of hi-fi model having the hi-fi IC, the audio output signal and the output signal of the SIF OUT pin are input to the A/V block. For this end, it is preferable that the audio output pin (AUDIO OUT) and the SIF OUT pin are adjacently disposed. Accordingly, a circuit construction on a printed circuit board, in which the tuner block  150  and the A/V block are mounted, becomes simpler. 
   Since the SIF OUT pin and the clock input pin (X-TAL IN) are respectively disposed at pin  13  and pin  7 , the two pins are disposed to have an interval of six pins. Since the clock signal (X-TAL IN) and the sound sub-carrier (SIF OUT) are high frequency signals, where the SIF OUT pin and the clock input pin (X-TAL IN) are adjacently disposed to each other, the clock signal and the sound sub-carrier badly influence each other. Therefore, the SIF OUT pin and the clock input pin (X-TAL IN) are preferably disposed as far from each other as possible. According to the present invention, the position of the clock input pin (X-TAL IN) has been moved to pin  7 , which is the farthest pin from the SIF OUT pin  13  among the pins ( 7 ,  11  and  15 ), which are not used in the conventional tuner block  50 . Thus, although the SIF OUT pin and the clock input pin (X-TAL IN) are closer by 1 pin than in the conventional tuner block  50 , an interval large enough to prevent interference from being generated between the pins has been maintained, and the number of the pins required to be moved in order to interconnect the tuner block  150  is minimized 
   Furthermore, as described above, to maintain the interval between the SIF OUT pin and the clock input pin (X-TAL IN), and the interval between the audio output pin (AUDIO OUT) and the video output pin (VIDEO OUT), the SIF OUT pin is preferably disposed between the audio output pin (AUDIO OUT) and the video output pin (VIDEO OUT). In other words, in the present invention, the SIF OUT pin and the audio output pin (AUDIO OUT) are not disposed at pin  12  and pin  13 , respectively, but are disposed at pin  13  and pin  12 , respectively. According to the above arrangement, the audio output pin (AUDIO OUT) and the video output pin (VIDEO OUT) are disposed to have the interval of four pins as described above, thus the AUDIO OUT pin and the VIDEO OUT pin are 1 pin further apart than in the conventional tuner block  50 . Moreover, according to the above arrangement, also the SIF OUT pin and the clock input pin (X-TAL IN) are disposed to have the interval of six pins. 
   An automatic fine tuning pin (AFT) is used by the tuner. Thus, it is preferable that the automatic fine tuning pin (AFT) is disposed with other pins (pin  6  through  10 ) which are also used by the tuner, thus, the AFT pin is disposed at pin  11 . 
   Other pins excluding the pins moved as described above have been arranged as in the conventional tuner block  50  to minimize the change of the position of the pins compared with the conventional tuner block  50 . 
     FIGS. 6A and 6B  show a switching circuit of the printed circuit board  200 , on which the tuner block  150  in  FIG. 5  is mounted. The switching circuit shown in  FIGS. 6A and 6B , is manufactured to accommodate either the conventional tuner block  50  as shown in  FIG. 6A , or the tuner block  150  according to the present invention as shown in  FIG. 6B , on the printed circuit board  200 . 
   As shown in  FIGS. 6A and 6B , a clock signal input (X-TAL IN) line is connected with pin  7  and pin  13  through a first clock switch  211  and a second clock switch  212 . Where the conventional tuner block  50  is mounted on the printed circuit board  200 , the first clock switch  211  is off and the second clock switch  212  is on as shown in  FIG. 6A . Where the tuner block  150  of the present invention is mounted on the printed circuit board  200 , the first clock switch  211  is on and the second clock switch  212  is off as shown in  FIG. 6B . 
   An ATF output line is connected with pin  21 , and connected with pin  11  via an AFT switch  220 . Where the conventional tuner block  50  is mounted on the printed circuit board  200 , the AFT switch  220  is off as shown in  FIG. 6A , and where the tuner block  150  according to the present invention is mounted on the printed circuit board  200 , the AFT switch  220  is on as shown in  FIG. 6B . 
   An SIF output line (SIF OUT) is connected with pin  20  and connected with pin  13  via an SIF switch  240 . Where the conventional tuner block  50  is mounted on the printed circuit board  200 , the SIF switch  240  is off as shown in  FIG. 6A , and where the tuner block  150  according to the present invention is mounted on the printed circuit board  200 , the SIF switch  240  is on as shown in  FIG. 6B . 
   A video signal output line (VIDEO OUT) is connected with pin  22  and connected with pin  16  via a video switch  250 . Where the conventional tuner block  50  is mounted on the printed circuit board  200 , the video switch  250  is off as shown in  FIG. 6A , and where the tuner block  150  according to the present invention is mounted on the printed circuit board  200 , the video switch  250  is on as shown in  FIG. 6B . 
   An electrical power supply line (Vcc 5V) is connected with pin  3 , and an audio output (AUDIO OUT) line is connected with pin  19 . The electrical power supply line (Vcc 5V) and the audio output (AUDIO OUT) line are connected with pin  12  through a conversion switch  230 . Where the conventional tuner block  50  is mounted on the printed circuit board  200 , the conversion switch  230  is switched to connect pin  12  with the electrical power (Vcc 5V) as shown in  FIG. 6A , and where the tuner block  150  according to the present invention is mounted on the printed circuit board  200 , the conversion switch  230  is switched to connect pin  12  with the audio output (AUDIO OUT) line as shown in  FIG. 6B . Therefore, where the conventional tuner block  50  is mounted, the electrical power is supplied to the modulator through pin  12 , and where the tuner block  150  according to the present invention is mounted, the audio signal output through pin  12  is transmitted to the A/V block. 
   Each of the switches  211 ,  212 ,  220 ,  230 ,  240  and  250  is realizable by using a jumper which determines an electrical connection status on the printed circuit board  200 . In other words, by changing the installation position of the jumper installed on the printed circuit board  200 , the electrical connection status between the parts mounted on the printed circuit board  200  is changed. Therefore, without changing the arrangement of holes which are formed on the printed circuit board  200  for mounting the tuner block, the electrical connection status of the printed circuit board  200  is changeable to be used with either the conventional tuner block  50  or the tuner block  150  according to the present invention. 
   One way of changing the electrical connection status is to change a jumper installation program of a chip mounting apparatus. Another way of changing the electrical connection status is to manufacture the printed circuit board  200  to include the switches  211 ,  212 ,  220 ,  230 ,  240  and  250 , and allow the switching status to be changed in accordance with the mounted tuner block selected from one of the conventional tuner block  50  and the tuner block  150  according to the present invention. Consequently, the tuner block  150  may be used interchangeably with the conventional tuner block by appropriately setting the switches  211 ,  212 ,  220 ,  230 ,  240  and  250  as described above. 
   Since the electrical power for supplying the electrical power to the modulator and the tuner is provided by a common pin (pin  3 ) in the tuner block  150 , the number of the pins is reduced, and a small-sized tuner block compared to the conventional tuner block may be manufactured. 
   Moreover, each pin of the tuner bock  150  is disposed to correspond to the position of the modulator IC and the integrated tuner and IF/demodulator circuit IC disposed in the casing, thus the tuner block is compact, and at the same time, the circuit construction in the casing is simplified. In addition, the noise and interference between the signals in the tuner block  150  is minimized. 
   Furthermore, by changing installation positions of jumpers in the printed circuit board, one of the conventional tuner block and the tuner block according to the present invention is selectively installable. Compared with the conventional tuner block  50 , the number of the pins changed to result in the tuner block  150  is minimized, thus the number of jumpers which are changed in position is reduced. 
   Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.