JPS6236389Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement in the self-test function of a still image receiver.

Conventional still image transmission systems are self-tested by connecting external equipment such as modem testers and test signal generators.

Therefore, there was a drawback that test equipment had to be prepared and connected each time a test was performed.

The purpose of this invention is to use the modulation section of the modem to eliminate the above-mentioned drawbacks, and to provide the receiver itself with a self-test function by creating a test signal using the modem's reception timing signal (RT). There is a particular thing.

FIG. 1 shows an embodiment of the present invention, in which 1 is a received signal input terminal, 2 is a switch, 3 is a modem demodulator, 4 is received data (RD), 5 is a received timing signal (RT), and 6 is a received signal input terminal. A still image receiving section, 7 is an image output terminal, 8 is a frequency dividing circuit, 9 is a test signal, and 10 is a modulation section of the modem. Figure 2 shows the RT5 shown in Figure 1.
and the waveform of the test signal 9. FIG. 3 shows a part of one line of the signal waveform obtained at the image output terminal 7 during the self-test.

Next, the operation of the present invention will be explained. A signal from a line is connected to a received signal input terminal 1 in FIG. 1, and a switch 2 normally selects the signal from the line and supplies it to a demodulator 3 of the modem. RD4 and RT5 are applied from the demodulator 3 of the modem to the still image receiver 6, where the DPCM signal is decoded and returned to an image signal, which is output to an image signal output terminal 7. mentioned above
RT5 is also added to the frequency dividing circuit 8, and the frequency dividing circuit 8 divides RT5 into 1/the number of DPCM quantizations. If we take the case where 4-bit DPCM encoding is currently being performed as an example, as shown in Figure 2,
RRT5 is frequency-divided by 4 and becomes test signal 9. The test signal 9 is applied to the modulation section 10 of the modem shown in FIG. 1, and the modem modulation output is applied to the modulation section of the modem by switching the switch 2 during a self test.

The period divided by the broken line in Figure 2 is calculated per pixel.
If DPCM encoding is used, the 4-bit data string is 1001
This means a plus 1 level command. DPCM
In the case of encoding, one line of a television signal or one line divided into several units is used as a unit, and the first data is transmitted as a PCM signal as an initial value. If the initial value is an 8-bit PCM signal, the data string will be 2 sections of the test signal,
It becomes 10011001. FIG. 3 shows a part of the signal obtained at the image output terminal 7 during the self-test. An initial value V is obtained at the beginning of the television signal line, and subsequent signals are decoded to plus one level by the DPCM code 1001, resulting in a toothed waveform. By connecting this signal to a TV monitor,
It is possible to check whether there are data errors.

What has been described above is one embodiment of the present invention, and various types of test signals can be created by combining data of the DPCM period or by periodically inverting the data.

As explained above, according to the present invention, a still image receiver can be self-tested without using external test equipment. Furthermore, it is also possible to use the signal from the address counter of the receiver as a means for obtaining the test signal, which is highly effective in practice.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, FIG. 2 shows a test waveform diagram, and FIG. 3 shows a waveform showing part of a television signal obtained during a self-test. 3: Demodulation section, 4: Reception data, 5: Reception timing signal, 6: Still image reception section, 8: Frequency division circuit, 1
0: Modulation section.

Claims (1)

[Scope of utility model registration request] A still image transmission device that encodes a television image signal with DPCM and transmits it using a modem, which includes a modem that includes a modulation section and a demodulation section, and a modem that encodes a reception timing signal of the modem by dividing the number of quantizations in DPCM encoding.
a frequency divider circuit that divides the frequency into a frequency divider, and a switch that selects either a modulated signal by adding the output of the frequency divider circuit to a modulation section of the modem or an external input signal and applies it to the demodulation section. 1. A still image receiver, wherein the output of the modulation section is selected as the input of the demodulation section during a self-test.