JPH0993342A - Transmission and loop detection circuit for high output signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a subscriber testing device by using a subscriber circuit to detect transmission of a howler tone and a looping at the transmission of the howler tone. SOLUTION: In the case of sending a howler tone to a telephone set 3, a howler tone subject to PCM processing from a digital tone source circuit 32 of a host device 30 is sent to a CODEC, D/A converted therein and the analog signal is given to a hybrid circuit (HYB). The HYB amplifies the howler tone under the control of the host device and the amplified tone is sent to the telephone set 3 via a feeding monitor circuit 11 having high output impedance. The feeding monitor circuit 11 detects a loop of a subscriber line N. No looped line (on-hook state of telephone set) is identified by monitoring a detection signal (SCN) with an SCN monitor circuit 31 of the host device to stop the transmission of the howler tone from the digital sound source circuit 32. The SCN circuit 31 and the digital tone source circuit 32 may be provided in a subscriber circuit 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for sending out a large output signal such as a howler sound and a loop detection circuit using a subscriber circuit used in an exchange or the like.

[0002]

2. Description of the Related Art A conventional howler sound transmission and loop detection circuit will be described with reference to FIG. The subscriber line test apparatus 20 is connected to the subscriber line N via a switch 23,
The howler sound sending device 22 sends out howler sound, the subscriber line monitoring device 21 monitors the subscriber line (including loop detection at the time of sending out howler sound), and the power feeding source 26 joins via the feeding resistors 24 and 25. Power is being supplied to the private line N.

[0003]

Recently, in order to miniaturize the subscriber line test apparatus 20, there is a new problem that the subscriber circuit is required to perform the howler sound transmission and the loop detection at the time of the howler sound transmission. It has occurred. The present invention aims to solve such a new problem.

[0004]

A high output signal sending and loop detecting circuit of the present invention is a PCM signal sent from a digital sound source of a higher order device of a subscriber circuit to a receiving highway, or a PCM signal in the subscriber circuit. The PCM signal read from the memory is D /
A-converted, further amplified by the HYB circuit, sent out a large output signal such as howler sound, ringing signal, etc. to the telephone via the power supply monitoring circuit, loop detection of the subscriber line is performed by the power supply monitoring circuit, and the loop A detection signal (also referred to as an SCN signal) is monitored by a host device or a subscriber circuit, an on-hook / off-hook is detected, and transmission of a high output signal is stopped.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention is shown in FIG. The subscriber circuit 10 has a plurality of types of subscriber-related functions, but FIG. 1 describes only the functions necessary for transmitting the howler sound and detecting the loop. The power supply monitoring circuit 11 is a power supply 14
Is used to supply a call current to the telephone 3, relay a large output signal such as a howling sound to the telephone, and monitor the subscriber line N. The SCN signal 15 is sent to the SCN monitoring circuit 31 of the host device 30 via the transmission highway 1. PCM
Encoder / decoder (hereinafter codec; abbreviated as CODEC) 1
3 performs A / D conversion or D / A conversion with a 2-line to 4-line conversion circuit (hereinafter abbreviated as HYB) 12. The HYB 12 performs matching termination with respect to the subscriber line N at the voice signal frequency during normal operation, but does not perform matching termination under control of the host device or the subscriber circuit at the time of sending out howler sound and is input from the codec 13. The signal is amplified and sent to the telephone 3 via the power supply monitoring circuit 11 and the subscriber line N. The digital sound source circuit 32 sends out a PCM Haula signal to the codec 13 via the reception highway 2. (Embodiment 1) An operation at the time of transmitting a howler sound will be described with reference to FIG. 1B. A Howler signal having a digital data structure converted into PCM from a digital sound source circuit 32 in a host device 30 of the subscriber circuit 10 is input to a codec 13 via a receiving highway 2, D / A converted, and sent to a HYB 12. The signal level of the howler sound applied to the telephone 3 is considerably higher than that of the voice signal, so when transmitting the howler sound, HYB1
At 2, the howler signal is amplified, and the amplified howler sound is sent to the telephone 3 via the power supply monitoring circuit 11. At that time, since the feedback signal becomes large, the howler sound is transmitted with high impedance without performing matching termination. Since there is no signal sent from the telephone 3 when the howler sound is sent, there is no problem even if matching termination is not performed.

At this time, the loop of the subscriber line N is detected by using the conventional loop detection circuit 11a of the power supply monitoring circuit 11. The SCN signal output from the loop detection circuit is normally at L (low) level in the off-hook state and H level in the on-hook state.
(High) level. Since the Howler signal level is high, it may exceed the detection threshold level as shown in FIG. 1B, and the loop detection circuit may erroneously detect. So SCN signal 1
5 is sent to the higher-level device 30 via the transmission highway 1, and the SCN signal is monitored there, and at regular intervals (for example, 10 m
It is possible to easily determine the presence / absence of a loop in the subscriber line by obtaining the duty ratio (for each s) and determining that there is no loop when the duty ratio is 100% and that there is a loop when the duty ratio is 100% or less.

In FIG. 1B, when the off-hook state is changed to the on-hook state, even if the howler signal from the digital sound source circuit 32 comes to the HYB 12, the power feeding monitoring circuit 1
The bias current of 1 stops flowing, and the DC current and the Howler signal are not transmitted from the power supply monitoring circuit 11 to the telephone 3. After that, when the SCN monitoring circuit 31 determines that there is no loop, the transmission of the howler signal from the digital sound source circuit 32 is stopped.

The SCN monitoring circuit 31 may be provided in the subscriber circuit 10. The digital tone generator circuit 32 can also be built in the subscriber circuit 10 by storing digital data in a memory in the subscriber circuit 10. (Embodiment 2) Next, a second embodiment will be described. Although the circuit configuration is the same as that of FIG. 1A, a D / A conversion means of the HYB 12 or the codec 13 or a means for controlling the sending and stopping of the howler sound is further provided in the host device 30, and the howler sound is intermittently connected to the subscriber line N. Send to. The relationship between the output waveform of the howler sound and the SCN signal 15 in the second embodiment is shown in FIG. SC
In the N monitoring circuit 31, the SCN signal 15 is monitored during the howler sound stop period Ts, and the level of the SCN signal 15 (L, L,
The presence / absence of a loop can be discriminated from H). With such a configuration, means for removing the AC signal component of the howler sound and extracting only the DC signal component in the loop detection circuit 11a becomes unnecessary, and the circuit can be downsized.

In the first and second embodiments, the transmission of the howler sound has been described as an example, but it is obvious that the present invention can be applied not only to the howler sound but also to a large output signal such as a ringing signal.

[0010]

As described above, according to the present invention, it is possible to easily perform the transmission of a large output signal such as a howler sound by using the subscriber circuit and the loop detection at the time of transmitting the large output signal.
Therefore, by deleting these functions from the subscriber line test device, the device can be downsized.

[Brief description of drawings]

FIG. 1A is a block diagram showing an embodiment of the present invention, and B is a timing chart showing an example of A.

FIG. 2 is a timing chart showing another example of FIG. 1A.

FIG. 3 is a principle circuit diagram of a conventional large output signal transmission and loop detection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 000005223 4-1 1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor Yoshinori Oikawa 1-1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihonhon Telegraph and Telephone Corporation (72) Inventor Seiichi Yamano 1-1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor, Isamu Ueki 5-7-1, Shiba, Minato-ku, Tokyo NEC Incorporated company (72) Masayuki Sakai, 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Incorporated in the Information and Communication Division, Hitachi, Ltd. (72) Inventor Takashi Kato 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industrial Co., Ltd. (72) Inventor Hiroshi Shinkawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (2)

[Claims] 1. A high output signal sending and loop detecting circuit for sending a high output signal such as a howling sound or a ringing signal to a telephone to detect a loop of a subscriber line, the loop detecting circuit being provided in the subscriber circuit, Means for digital-to-analog conversion of a PCM signal sent from the digital sound source of the host device on the highway or a PCM signal read from the memory in the subscriber circuit, and provided in the subscriber circuit and converted into an analog signal. A two-wire to four-wire conversion means for amplifying the PCM signal under the control of the host device or the subscriber circuit and sending it to the subscriber line through the power supply monitoring circuit in the subscriber circuit with high impedance without performing matching termination. (HYB), and loop detection means provided in the power supply monitoring circuit in the subscriber circuit and for detecting a loop of the subscriber line. A high output signal transmission and loop detection circuit characterized by the following. 2. A control means for sending / stopping the large output signal is provided in the digital / analog converting means or the two-wire / four-wire converting means to intermittently send the large output signal, and the interval of the large output signal. 2. The large output signal transmission and loop detection circuit according to claim 1, wherein loop detection is performed from the output of the loop detection means during the period.