JPH03209955A - Sound recording/reproducing telephone set - Google Patents

Abstract

PURPOSE:To prevent the reduction of a circuit scale and the deterioration of a tone quality caused by curtailing remarkably an analog circuit by providing a means for executing direct compression encoding from a PCM signal, and a means for executing decoding to the PCM signal. CONSTITUTION:As for PCM signals P1 of 64kbps outputted from an interface circuit 1, one of them passes through a switching circuit 4 and is outputted to a CODEC 3, converted to an analog signal and converted to an acoustic signal by a receiver of a handset 6 through a speech circuit 5. On the other hand, the other passes through the circuit 4 and is sent as a PCM signal P3 to a compression encoding/decoding circuit 7, and simultaneously stored in a memory 8. Subsequently, at the time of sound-recording an answer message, etc., they pass through the circuit 5, the CODEC 3 and the circuit 4 from a transmitter of the handset 6 and are sent to the circuit 7, and stored in the memory 8. On the contrary, at the time of reproducing the contents stored in the memory 8, a digital signal read out of the memory 8 is converted to the PCM code P3 by the circuit 7, and sent out to the circuit 1 or the CODEC 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording and reproducing telephone, and more particularly to a recording and reproducing telephone that performs digital recording and reproducing of audio signals using ISDN.

[Conventional technology]

Currently, digital telephones using such ISDN are being put into practical use, and telephones with a built-in voice recording and playback function are also being developed.

For example, among analog subscriber line telephones, telephones with a digital audio recording and playback system have been put into practical use as answering machines. This allows the bit rate to be increased to 32% using the adaptive delta modulation method (ADM) directly from the analog signal.
It converts into a digital signal of k bps to 8 k bps, and records this converted digital signal in a memory such as RAM, while when playing back the digital signal read from the memory is returned to an analog signal by D/A conversion. It is a method. Therefore, a noise removal filter and a filter for preventing aliasing distortion are required at the analog signal input and output ends. Hereinafter, such conventional technology will be described as ISDN.
The case where this method is applied to a digital telephone will be explained.

FIG. 3 is a block diagram of a conventional recording and reproducing telephone set.

As shown in FIG. 3, the conventional recording/playback digital telephone has an interface circuit 1 for the S reference point of ISDN, which is an interface with a 4-wire digital service unit (not shown) connected to the line.
, a control circuit 2 that supports the communication procedure (layer 2 or layer 3) based on the CCITT recommendations and is operated by input from the keyboard 9, and conversion of the PCM signal from the interface circuit 1 to the analog audio signal A1. codec 3 for performing analog audio signal A1. A
2. Compression encoding/encoding/compression encoding/encoding/encoding/encoding/decoding transmission/reception of analog signal A2 between the switching circuit 4 that switches the signal route of A, the communication circuit 5 connected to the handset 6, and the switching circuit 4 using the ADM method. It has a decoding circuit 7 and a memory device 8 for storing and reading digital data between the decoding circuit 7 and the circuit 7.

In a telephone with such a configuration, when recording the other party's voice via a four-wire wire (not shown), the analog output A1 of the codec 3 is sent to the compression encoding/decoding circuit 7 via the switching circuit 4, and is stored in the memory. 8 as a digital signal.

On the other hand, when reproducing the digital signal stored in the memory 8, the digital signal read out from the memory 8 is sent to the compression encoding/decoding circuit 7, and the analog signal A
2 and send it to the communication circuit 5 as an analog signal A3, or send it to the communication circuit 3 as an analog signal A1.
Send it out as.

Here, the control circuit 2 that controls the operations of the switching circuit 4 and the compression encoding/decoding circuit 7 is controlled by input from the keyboard 9.

Also, when recording message information etc. from the handset 6 to the memory 8, codec 3. Recording is performed via the switching circuit 4 and the compression encoding/decoding circuit 7.

[Problem to be solved by the invention]

The conventional recording/playback telephone described above has many circuits that handle analog signals. That is, the codec, switching circuit, and compression encoding/decoding circuit all have analog signal transmitting/receiving circuit sections.

5- Therefore, many parts such as coupling capacitors are required, and analog filters are also required in the codec and compression encoding/decoding circuit to prevent aliasing distortion and reduce unnecessary band noise.

This increases the overall circuit scale and has the disadvantage that it is not possible to reduce the cost of the device.

On the other hand, when recording audio sent through a line,
Since the codec converts the signal back to an analog signal and then compresses and encodes it, the problem is that the sound quality deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide a recording/playback telephone that can reduce the circuit size and cost, and prevent deterioration in sound quality when recording audio signals sent through a line.

[Means to solve the problem]

The recording and playback telephone of the present invention includes an interface circuit for line connection, a codec connected to the speech circuit,
a switching circuit that switches between the 6 PCM signals from the interface circuit and the PCM signals from the codec; and a compression encoding/decoding circuit that compression encodes the PCM signal from the switching circuit and decodes data from the memory into a PCM signal. and a control circuit that is driven from the keyboard and controls at least the interface circuit, the switching circuit, and the compression encoding/decoding circuit.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a recording/playback telephone showing a first embodiment of the present invention.

As shown in FIG. 1, in this embodiment, a transformer 10.
An interface circuit 1 connected via 11 and an interface circuit 1 driven by a keyboard 9
A control circuit 2 that controls each circuit including the codec 3 that is connected to a communication circuit 5 connected to a handset 6, and a synchronization signal S from the interface circuit 1.
A switching circuit 4 switches transmission and reception of the CM signal P1 and transmission and reception of the PCM signal P1 to and from the codec 3, and a PCM signal sound 3 from the switching circuit 4 is compressed and encoded and stored in a memory 8, and the data from the memory 8 is converted into a PCM signal. It has a compression encoding/decoding circuit 7 that encodes signal tones, and a speech synthesis circuit 12 that is controlled by the control circuit 2 and outputs a PCM signal.

Next, the operation of the above-mentioned recording/playback telephone will be explained.

First, 6 4 is output from the interface circuit 1.
One of the k bps PCM signals P1 is outputted to the codec 3 through the switching circuit 4, converted into an analog signal, and converted into an audio signal by the telephone receiver of the handset 6 via the telephone communication circuit 5. The other PCM signal tone 3 is sent to the compression encoding/decoding circuit 7 through the switching circuit 4 and is simultaneously stored in the memory 8.

Next, when recording a response message, etc., from the transmitter of the handset 6 to the telephone circuit 5. Codec 3. The signal is sent through the switching circuit 4 to the compression encoding/decoding circuit 7 and stored in the memory device 8.

Conversely, when reproducing the contents stored in the memory 8, the digital signal read out from the memory device 8 is converted into PCM code P3 by the compression encoding/decoding circuit 7,
The signal is sent to the interface circuit 1 or the codec 3.

Furthermore, the output of the speech synthesis circuit 12 controlled by the control circuit 2 can be processed in the same way by providing a PCM output, that is, a PCM signal.

However, regarding compression encoding/decoding technology, A
The technology already developed for DPCM etc. can be reused, and the analog part only needs to be the communication circuit 5.

FIG. 2 is a block diagram of a recording/playback telephone showing a second embodiment of the present invention.

As shown in FIG. 2, this embodiment is an example in which a synchronization circuit 13 is added to the first embodiment described above. The operation of the nine telephones is similar to that of the first embodiment. That is,
In FIG. 1, a synchronization signal S is transmitted from an interface 1 to a compression encoding/decoding circuit 7. Codec 3. Speech synthesis circuit 1
The signals sent to the 2nd etc. are summarized and the synchronous circuit 1
3, it is configured to be synchronized with the interface circuit 1. In this embodiment as well, since direct compression encoding and reverse decoding can be performed from a PCM signal, the analog portion of each circuit can be reduced.

In this manner, according to the two embodiments described above, it is possible to directly compress and encode a PCM signal (digital signal), and also to directly decode a PCM signal.

〔Effect of the invention〕

As explained above, the recording and playback telephone of the present invention can be
By having a means for directly compressing and encoding an M signal and a means for decoding it into a PCM signal, it is possible to reduce the circuit scale and prevent deterioration of sound quality due to a significant reduction in the number of analog circuits.

10-

[Brief explanation of drawings]

FIG. 1 is a block diagram of a recording/reproducing telephone showing a first embodiment of the present invention, FIG. 2 is a block diagram of a recording/playing telephone showing a second embodiment of the present invention, and FIG. 3 is a block diagram of a conventional example. 1 is a block diagram of a recording and playback telephone shown in FIG. 1... Interface circuit, 2... Control circuit, 3
... Codec, 4... Switching circuit, 5... Call circuit, 6... Handset, 7... Compression encoding/decoding circuit, 8... Memory, 9... Keyboard, 10. 1
1...Transformer, 12...Speech synthesis circuit, 13...
- Synchronous circuit, P1 to P4...PCM signal, S...synchronous signal.

Claims (3)

[Claims] (1) An interface circuit for line connection, a codec connected to a communication circuit, a PCM signal from the interface circuit, and a PC from the codec.
A switching circuit that switches the M signal, etc., and a P signal from the switching circuit.
Compress and encode the CM signal and send the data from the memory to the PC.
A recording/reproducing device comprising: a compression encoding/decoding circuit for decoding into an M signal; and a control circuit driven by a keyboard and controlling at least the interface circuit, the switching circuit, and the compression encoding/decoding circuit. telephone. (2) The recording and reproducing telephone according to claim 1, wherein a voice synthesis circuit is connected to the switching circuit and is controlled by a control circuit. (3) an interface circuit for line connection, a codec connected to the communication circuit, a synchronization circuit that receives a synchronization signal and a PCM signal from the interface circuit, and a PCM signal from the synchronization circuit and a PCM signal from the codec. a switching circuit for switching signals, etc.; a compression encoding/decoding circuit for compressing and encoding the PCM signal from the switching circuit and decoding data from the memory into a PCM signal; and the interface circuit and the switching circuit driven by the keyboard. 1. A recording and reproducing telephone comprising a circuit and a control circuit for controlling at least a compression encoding/decoding circuit.