Digital subscriber line transmission system

[Detailed Description of the Invention]

[Summary of the Invention] In the time compression multiplex (Bing Bong transmission method) to which the digital subscriber circuit (DLC is called below) connected by the 2 line type subscriber line and the device in a house send out a burst signal a predetermined cycle in time sharing mutually, The outgoing level of the burst signal which DLC sends out is changed according to the length of a subscriber line way, and reduction in cross-talk and reduction of power consumption are aimed at. [Industrial Application] The present invention relates to a time compression multiplex (ping-pong transmission power type), It is related with the digital subscriber line transmission method to which the outgoing level of the burst signal (an office burst signal is called below) include data signal DO transmitted is changed according to the length of a subscriber line way from the network of the switchboard which DLC sends out. The transmission method of a subscriber line is also beginning to be digitized with progress of digital exchange art in recent years. As this transmission method, what is called a ping pong transmission system is adopted, and an office burst signal is sent from DLC to every predetermined cycle (burst cycle) at the device in a house, From the device in a house, after receiving an office burst signal, the burst signal (a member burst signal is called below) include data signal DS transmitted from the terminal unit of the device in a house takes an office burst signal and a synchronization, and is returned to D-LC. In this case, an office burst signal is although it is sent out to a subscriber line with a fixed outgoing level, Since a large majority of member is concentrated on a sufficiently near distance, offer of a digital subscriber line transmission method from which it may cross-talk to other subscriber lines in the outgoing level united with the distant member, and the above-mentioned outgoing level changes with subscriber line length since power consumption is also uneconomical is demanded. [Description of the Prior Art] Drawing 4 is an explanatory view of the digital subscriber line transmission method of a conventional example, and Drawing 5 is a transmission explanatory view of an office burst signal and a member burst signal. If it is in this conventional example, 192K bps is adopted as a data-communications speed of a ping pong transmission system, and the burst cycle has become 125 microseconds. 5.2 microseconds are taken as a time slot and the 1 Ba 1 strike cycle consists of 24 time slots. Data signal DO of 8 A bit sent to DLC1 from a network of a switchboard is transmitting circuit 15, and is a frame signal showing a head position of a burst signal. 1 A bit of frame bit F by which numerals "0" and "1'' are repeated by turns for every burst signal, Direct-current balance and 1 A bit of Tut B which are added so that numerals "1" in a burst signal may become even number are added, and it becomes an office burst signal (frame form) of 10 A hit, and is changed into bipolar signal form. The timing signal of timing circuit 17 which an outgoing level is set up with transmitting driver 11 with which the office burst signal changed into bipolar signal form consists of transistor 111,112, and determines the sending-out time of an office burst signal, It is sent out to subscriber line 3 via transformer 19 for every burst cycle shown in Drawing 5. Here, VCC shows a power supply. Each burst signal of Drawing 5 is expressed in frame form for convenience, although transmitted by a bipolar signal in a subscriber line. Also digital line termination device (DSU is called below) 21 of device 2 in a house, To data signal DS of 8 A bit transmitted from terminal unit (DTE is called below) 22, Like explanation of the above-mentioned office burst signal, frame bit F of 1 A bit and direct-current balance bit B of 1 A bit are added, the member burst signal (frame form) of 10 A bit is generated, and it synchronizes with the end of reception of an office burst signal, A member burst signal is sent out to subscriber line 3 in bipolar signal form. The member burst signal of bipolar signal form is received via transformer 19 in termination circuit 12, and is reproduced by the original member burst signal. Bit synchronization circuit 13 extracts a clock signal from a member burst signal, sends the clock signal to termination circuit 12, and makes it take the bit synchronization of the reproduced member burst signal, and it makes it send it out to receiving circuit 16. From the member burst signal with which, as for frame synchronization circuit 14, the above-mentioned clock signal and the bit synchronization were taken, The position of frame bit F which has repeated numerals "0" and "1" for every burst signal is extracted, the arrival time term of a member burst signal is detected, a frame synchronization is taken, and frame topology is sent to receiving circuit 16. Receiving circuit 16 extracts data signal DS from a member burst signal except for frame bit F and direct-current balance bit B by the topology, and sends out data signal OS to a network according to the timing by the side of the switchboard of timing circuit 17. As shown in Drawing 5, DSU to which the office burst signal sent out from DLC reaches DSU in response to transmission delay sends out a member burst signal immediately after completing reception of an office burst signal, but the signal reaches DLC in response to transmission delay of a subscriber line. The difference of the end time of the office burst signal which DLC sent out, and the receiving time of onset of the received member burst signal is a transmission time delay of a subscriber line, and a transmission time delay becomes long, so that a subscriber line is long. [Problem(s) to be Solved by the Invention] If it is in the ping pong transmission system of a conventional example, the office burst signal sent out is sent with the fixed outgoing level irrespective of the distance on the device in a house from the switchboard. It is for this level securing the transmission characteristic in the longest subscriber line currently assumed, and to the short-distance subscriber line which most members are concentrating, since it is an unnecessarily high level, there is a problem that cross-talk and power consumption to other subscriber lines are uneconomical. [Means for Solving the Problem] Drawing 1 is a principle block diagram of the present invention. 1 degree of digital subscriber circuits are shown. A transmitting driver with which 2 sends out a device in a house, 3 sends out a subscriber line of a 2 line type, and 11 sends out office burst 1 A word, A termination circuit where 12 receives a member burst signal, a transformer by which 19 combines subscriber line 3, transmitting driver 11, and termination circuit 12, 20 is a synchronous circuit which extracts a clock signal from a member burst signal, detects a frame signal which shows a head position of a member burst signal to a member burst signal where a synchronization was taken by the clock signal in termination circuit 12, and detects an arrival time term of a member burst signal. As a thing concerning the present invention, 21 detects a transmission time delay by subscriber line 3 from sending-out time of an office burst signal, and an arrival time term of a member burst signal, A time delay detection means to judge subscriber line length, and 22 are switching means to which an outgoing level of transmitting driver 11 is changed by the judgment of time delay detection means 21. [Function] Digital subscriber circuit 1 * and device 2 in a house perform communication by a ping pong transmission system using an office burst signal and a member burst signal via member 'fa3. An outgoing level is set up with transmitting driver 11, and an office burst signal is sent via device 2 Hetranance 19 in a house, and subscriber line 3. Device 2 in a house sends out a member burst signal to subscriber line 3 immediately after the end of reception of an office burst signal. Termination circuit 12 receives a member burst signal via transformer 19, and sends it to synchronous circuit 20, and it makes a clock signal extract. After creating the member burst signal which was able to take the bit synchronization using the clock signal, the frame signal which shows the head position of a member burst signal again in synchronous circuit 20 is made to detect, and the arrival time term of a member burst signal is made to detect. The arrival time term of the member burst signal, it is sent to time delay detection means 21, it is compared with the sending-out time of an office burst signal, and a transmission time delay is found. When the regulation transmission time delay and the above-mentioned transmission time delay corresponding to subscriber line length of fixed length are compared and it is judged that it is more than a regulation transmission time delay, time delay detection means 21 starts switching means 22, changes the transmitting level of transmitting driver 11, and let it be a transmitting level according to the subscriber line length. Since the office burst signal of a proper level is sent out in this way to the short-distance subscriber line which most members are concentrating and the office burst signal of a proper level is sent out also to a long-distance member, cross-talk to other subscriber lines is lost and power consumption also decreases. [Example] An illustration example explains the present invention concretely below. It is a delay explanatory view of the member burst signal according [ Drawing 3 ] to subscriber line length according [ Drawing 2 ] to the explanatory view of the digital subscriber line transmission method of one example of the present invention. Passage same numerals show the same subject for a plan. In Drawing 2, bit synchronization circuit 13. frame synchronization Circuit worker 4 corresponds to synchronous circuit 20 of Drawing 1, flip-flop 23 corresponds to time delay detector circuit 21 of Drawing 1, and transistor 24. resistance R corresponds to cutting means 22 of Drawing 1. The transmission-and-reception operation of an office burst signal and a member burst signal in the present invention is the same as a conventional example. Although an office burst signal is sent out to subscriber line 3 via transformer 19 from transmitting driver 11 as the conventional example explained, Since power supply ■CC is supplied to transistor 111*112 of transmitting driver 11 via resistance R, the usual outgoing level is low and is a proper level at the subscriber line of the short distance. As shown in Drawing 3, when subscriber line length is Om, there is no transmission time delay by a subscriber line, After the end of sending out of an office burst signal, a member burst signal is received immediately in receiving circuit 16, and a member burst signal and output signal FS of the phase and the merit are given to Terminal of flip-flop J from frame synchronization circuit 14. When subscriber line length is lkr'n, transmission time delays by a subscriber line are about 6 microseconds between one of the two / Km. Since a burst signal goes back and forth by this transmission method, a transmission time delay of a member burst signal is set to about 12 microseconds. Therefore, after office burst signal sending-out Hiragana, a member burst signal is delayed for about 12 microseconds, and is received in receiving circuit 16, and a member burst signal and output signal FS of the phase and the merit are given to Terminal of flip Float and f7' from frame synchronization circuit 14. Since the above-mentioned transmission time delay changes with subscriber line length, a regulation transmission time delay can be provided, and it can be judged by whether the time was exceeded or it does not exceed whether fixed subscriber line length was exceeded or it does not exceed. It is made to generate now in the position where the 13th time slot of a burst cycle begins delay judging timing pulse P in timing circuit 17, and the above-mentioned regulation transmission time delay is made to specify. If delay judging timing pulse P is given to terminal C of flip-flop 23 and output signal FS of frame synchronization circuit 14 is given to Terminal, the decision result about the above-mentioned subscriber line length will be outputted to output terminal Q, and the outgoing level of transmitting driver 11 will change with the outputs. That is, as shown in Drawing 3, output terminal Q of flip-flop 23 serves as a low level to the subscriber line length of about 870 m (10.4 microseconds of transmission time delays) in whom both delay judging timing pulse P (logic value 1) and output signal FS (logic value 1) exist, Since transistor 24 is not turned ON, an office burst signal is sent with the suitable outgoing level for the subscriber line of a short distance. When 870 m of subscriber line length pieces in which output signal FS (logic value 1) does not exist by delay judging timing pulse P (logic value 1) are exceeded, Since output terminal Q of flip-flop 23 becomes high-level, turns ON transistor 24 and short-circuits resistance R, The outgoing level of sending-out driver 11 goes up, and the level of the bipolar signal which was changed from the office burst signal and which is not illustrated becomes high, and is sent with the suitable outgoing level for a long-distance subscriber line. [Effect of the Invention] Like explained to details above (since the outgoing level of an office burst signal is changed to a suitable level by the merits and demerits of subscriber line length if it is in the present invention, cross-talk to other subscriber lines can be eliminated and power consumption can be decreased.) It is a delay explanatory view of the member burst signal according [ Drawing 3 ] to subscriber line length according [ Drawing 2 ] to the explanatory view of the digital subscriber line transmission method of one example of the present invention, and, in Drawing 4, Drawing 5 of a digital subscriber line transmission method of a conventional example is a transmission explanatory view of an office burst signal and a member burst signal. in a figure -- 1 -- * -- a digital subscriber circuit, 2 -- the device in a house, and 3 -- as for a transformer and 20, a transmitting driver and 12 are [ a time delay detector circuit and 22 ] switching means a synchronous circuit and 21 a termination circuit and 19 a subscriber line and 11.