DE1090726B - Multi-channel telephone system for intermittent transmission of several simultaneous messages over the same line - Google Patents

Description

GERMAN

The invention relates to a multichannel telephone system for the intermittent transmission of several simultaneous messages on the same line.

It is already a telephone system for reducing the frequency bandwidth required for transmission known, in which the voice frequency band is divided into several sub-frequency ranges and only these sub-areas are transferred alternately one after the other after they are in the same length laterally Sections have been subdivided, only part of which is transmitted. In this known system However, the duration of such a transmission segment is only V «o seconds, so that the speech, in particular in terms of plosives at which transmission is deteriorated. Furthermore are systems for multi-channel transmission are already known, in which the messages of the individual channels are temporally divided by periodically extracted from the speech streams and elements are transmitted alternately side by side while reducing the time by means of frequency multiplication, whereby There are transmission gaps in the individual channels on the receiving side. However, with these Systems increase the frequency range of the language required for transmission and the quality of the transmission also severely impaired by the transmission gaps.

The multi-channel telephone system according to the invention is distinguished from the known systems characterized in that the speech streams of each channel on the transmission side in at least two sub-frequency ranges are divided and, with interchangeable interchanges, the different speech streams at the same time Subranges of different channels are transmitted while maintaining their original frequency position and that on the receiving side the speech streams of the sub-areas of each channel are combined and the resulting time gaps by repeating those received immediately before and stored speech streams can be filled in.

In the system according to the invention, a high degree of secrecy is guaranteed because the speech streams of the individual channels on the common transmission line are mixed together. Furthermore, in addition to the frequency and time division of the speech frequencies, it is also possible to arrange the individual sections in a different order.

According to a preferred embodiment of the invention, the telephone system is designed so that the duration of the intermittently transmitted message sections is in each case V12 to V25 seconds.

As a memory for the received messages from the multi-channel telephone system

for transferring in batches

multiple simultaneous messages

over the same line

Applicant:

Iwasaki Tsushinki Kabushiki Kaisha,
Tokyo

Representative: Dr. F. Zumstein, patent attorney,
Munich 2, Bräuhausstr. 4th

Claimed priority:
Japan October 26, 1953

Hideo Seki, Tokyo,
has been named as the inventor

cuts, a rotating, magnetizable recording medium is expediently used.

Finally, the telephone system can be designed with particular advantage so that on the transmission side by periodic switching by means of relays, which are generated by a square wave generator with below the Speech frequencies are controlled at a lying frequency, two signals from the speech streams of the two channels are picked out, which are mutually shifted in time by the duration of a message section, respectively partially contain the message content of both channels and after cropping one Signal through a low-pass filter to the lower part of the speech frequency range and the other signal transmitted through the bandpass filter to the upper part of this area together via the line and that on the receiving side the two signals are separated from one another by appropriate filters and are magnetically recorded on two disks driven jointly by a motor, of which the signals to fill in the between the message sections lying transmission gaps are each scanned by two magnetic heads offset from one another in the direction of rotation of the disks and by means of relays to the original voice streams

009 627/297

3 4

the currents corresponding to the two channels gap in a manner known per se with the

be set, with the motor and two relays topping up the previous interval of the speech stream feeding square wave generators that were stored. This is in Fig. 1 with

Side by an Ii transmitted by the transmitting side? and 2 R indicated. The storage takes place through

Synchronization signal are controlled. 5 recording heads (magnetic heads) on corresponding

The system according to the invention can be used as a »multiple recording medium and subsequent re-recording

Multiple telephone system with frequency change and long keying.

samer temporal subdivision «(» Frequency-age- An important mistake in this above-mentioned

native-slow-time-divisiontelephone-system «) or briefly known system consists in the fact that plosives

referred to as the "Fasit" system. Some at- io such as p, t, k, b, d and g are often omitted when

For example, embodiments of the invention, they are based on a transmission gap between two

described below with reference to the drawings. other intervals of the relevant channel

Fig. 1 shows the relationship between time and freefall, because their duration is often less than 40 milli-

sequence in a known two-channel system in which seconds is. But you can't foresee whether

the speech streams of two channels alternately cross these plosives into such gaps in transmission

will carry; fall.

Fig. 2 shows the relationship between time and Fre- This disadvantage is addressed by the invention for a

sequence eliminated in a two-channel system according to the invention two-channel system according to FIG. In Fig. 2 is

with intermittent transmission with frequency increase, similar to FIG. 1, the time t in along the abscissa

division into two sub-areas; Plotted 20 milliseconds, while the ordinate of the

Fig. 3 shows the relationship between time and Fre- frequency f corresponds to. In this case the language

frequency in a two-channel system with division into frequency band, each channel 1 or 2 is divided into two parts.

five sub-frequency ranges; divided from 0 to 1500Hz or from 1500 to

Fig. 4 shows the relationship between time and Fre- 3000 Hz, and with intermittent trust

sequence in a five-channel system, in which the five schung each at the same time a sub-frequency band each

Partial frequency ranges are arranged regularly; Channel. In this system, the

Fig. 5 shows a modification of the system after each point in time a partial frequency range of each

Fig. 4 with irregular frequency and Zeitver- channel transmitted over the line. Now embrace

division scheme, as it is, for example, for closing but short-lasting consonants, for example

treatment is required; 3 ° final sounds, a wider frequency range than sounds

Fig. 6 shows schematically the transmission side of a two with a longer duration. Accordingly, the fre-

channel system with division into two partial frequency components of the plosives in each of the

areas; contain both sub-frequency bands if the time-

Fig. 7 shows schematically a receiver for a borrowed subdivision with changing frequency dividers

System, the transmitter of which is shown in Fig. 6; 35 areas is done slowly enough. In this way

8 shows a diagram of a transmitter and the suppression of plosives is always received in

catcher of another two-channel system with tolerable limits,

development into two sub-frequency ranges; A two-channel system with division of the speech

Fig. 9 shows schematically the entire circuit diagram of the frequency band in more than two subbands is in

of a telephone system in which the 40 according to the invention is shown in FIG. 3, namely there are five partial fre-

so-called "Fasit" system is used. quenzbands provided. Although this system is one

Before going into detail on the representation of the invented number of filters and a complicated circuit

If a simple batch transfer system is required, the

known type as preparation for the later comprehensibility are nevertheless significantly improved,

purifications described. 45 However, if the number of filters is excessive

In Fig. 1, along the abscissa is time and along increases, then third is a deterioration because of the

the ordinate the frequency of a line to transition phenomena at the limit frequencies of the

transmitted speech streams from two channels.

The numbers 1 and 2 represent the speech streams. Furthermore, one can use a five-channel system

represent both channels. These are alternately 50 dividing the speech frequencies into five sub-bands

transmitted at constant intervals, for example obtained by only taking the current of a partial

transmits at intervals of 50 or 100 milliseconds on the band of each channel, as shown in Fig.4

Place of intervals of 125 microseconds, as shown with a regular frequency distribution scheme

is adjusted in conventional time division multiplex telephone systems.

where a frequency band is required. 55 Fig. 5 shows another example of a five-channel

that is wider than the frequency band of the system. In this case, the frequency wise and

human language. If, for example, a time-divided speech stream of the individual channels

Period of 80 milliseconds is selected, then it is distributed irregularly among each other, both with respect to

the first interval of 40 milliseconds borrowed in terms of time as well as in terms of frequency.

Voice streams of channel 1 filled up while the 60 This version is used for transmission

second interval of also 40 milliseconds for home calls, whereby the secret

the speech streams of channel 2 is filled. The posture is better than previously used

Speech streams of each channel are sent to the reception procedure.

catcher side by synchronized with the transmitter The following are various circuits

Relay disconnected and transmission gaps 65 can be described according to the invention,

of 40 milliseconds in each period. . -I ₁

Such interrupted language is badly used. Example

of course, which makes communication difficult. This one circuit diagram of a multi-channel telephone

Difficulty can be encountered and the mind system is shown in two diagrams. Fig. 6

Significantly improve the possibility if the transmission 70 shows the sending side and FIG. 7 the receiving side.

In these figures the reference numbers are as follows, used:

X, 2

111, 121, 211, 221, 113, 123, 213, 223, 12,

22, 17, 27,
114, 124, 214,
224, 116, 126,
216, 226

112, 212, 115, 215

122, 222, 125, 225

3, 7

4, 6

5

8th

Microphones

9

10, 20

14, 24
13, 23

15, 25

16, 26

Audio frequency amplifier
Low pass filter

Band pass filter

Square wave generators
relay

Transmission line
Selection circuit for the

Synchronization stream
engine
Listener

Magnetic disks
Recording heads
Readheads
Erase heads

In Fig. 6, microphones 1 and 2 generate speech streams with a frequency band from 0 to 1500 Hz passing through low pass filters 112 and 212 and from 1500 to 3000 Hz passing through band pass filters 122 and 222. The output currents of these filters are each combined with the output currents of the complementary filter of the other channel. These combined currents are periodically given at a constant frequency, for example at 20 Hz, by a mechanical or electrical relay 4 alternately on the line 5, this relay being controlled by a square wave generator 3. In this way, the line current during the first time span from 0 to 50 milliseconds is made up of the lower frequency subrange of channel 1 and the higher frequency subrange of channel 2. This frequency distribution is swapped as soon as the first 50 milliseconds are over, and the new distribution is left for the next time span of 50 to 100 milliseconds, as is shown in FIG. 2, for example.

Since the sub-frequency bands are periodically interchanged, the received speech streams are taken after allocation to the assigned channel and filling in the gaps with the sense of hearing as continuous speech, similar to television, where intermittent scanning is common is. The voice streams on the line can to some extent be viewed as encrypted, because the currents of both channels are mixed and their mutual relationship is periodically changed will.

In Fig. 7 it is shown how a square wave generator 7 and a motor 9 on the receiver side are controlled synchronously with each other, the synchronization currents from the selection circuit 8 can be removed. If necessary, the control can be carried out semi-independently by the rectified output stream of the interrupted speech is intermittently synchronized.

The received speech streams are temporally divided by the relay 6 and passed to the recording heads 13 and 23 , which are located on the edge of the magnetizable disks 14 and 24, which are arranged coaxially to the shaft of the motor 9 and are driven by it. The recorded speech streams are picked up by the scanning heads 15 and 25, for example delayed by 50 milliseconds against the incoming speech streams α and b. These two groups of currents are then each divided into two channels by filters (low-pass filters 115, 215 and band-pass filters 225, 125). Finally it results by summarizing

ίο the output current of the low-pass filter of the first Group with the output current of the bandpass filter of the second group of channel 1, which goes to the listener 10 leads. Similarly, by combining the output current of the band pass filter, the first Group with the output current of the low-pass filter of the second group of channel 2 received and to the listener 20 headed. When filling the transmission gaps the received interrupted speech is it is advantageous to have two scanning heads with an offset corresponding to 50 milliseconds delay at each of the two magnetizable disks and the output currents of the two scanning heads each Slice instead of combining the incoming speech streams with the output streams of the individual Combine scanning head.

In this embodiment, the speech streams are amplified by audio frequency amplifiers 111, 121, 211, 221, 113, 123, 213, 223, 12, 22, 17, 27, 114, 124, 214, 224, 116, 126, 216 and 226 . The recorded currents must be erased by the erase heads 16 and 26 after each revolution of the magnetizable disks.

Example 2

Another example of a circuit diagram of a multi-channel telephone system is shown in FIG. This system is improved over the previous one in that the number of filters and the Amplifier is decreased. The following description gives the details of such an arrangement.

The following reference symbols and numbers are used in FIG. 8:

I, 2 microphones

15, 25, 35, 45 .. Attenuators A ₁ B Speech currents from microphones 1 and 2

111, 113, 116, 117, 121, 123, 126, 127, 217,

227 amplifier

112, 114 low pass filter

122, 125 high pass filter

3, 7, 17 square wave generators

4, 6, 14, 16, 26,

36 relays

5 transmission line

8 Selection circuit for the synchronization current

9 engine

10, 20 listeners

II, 21 Magnetizable Discs

18, 28. . * Recording heads

12, 13, 22, 23 .. scanning heads

19, 29 erase heads

On the transmitter side, the speech streams A of channel 1 and B of channel 2 are sent with a bandwidth of 3000 Hz to the two continuing lines with constant interchanging by the relays 4 and 14, which are generated by a square wave generator.

rator 3 can be controlled with a frequency of, for example, 20 Hz. The upper of these two lines then carries speech streams in the raw sequence ABAB, for example exchanged every SO milliseconds, while the lower sequence is BABA . One of the two lines leads to a low-pass filter 112 from 0 to 1500 Hz and the other to a high-pass filter from 1500 to 2000 Hz. If the output currents of these two filters are combined, the result is the signal in line 5, as shown in FIG.

At the receiving end, the incoming speech streams are first fed into a low-pass filter 114 with a frequency range from 0 to 1500 Hz and into a high-pass filter 125 with a frequency range from 1500 ¹ to 3000 Hz. At the same time, a synchronization current supplied by the square wave generator 3 is separated by a selection circuit 8 and fed to a motor 9 in order to control it, and to the square wave generators 7 and 17, which in turn control the relays 6, 16, 26 and 36. These relays can be mechanical relays or tube relays, commutators or ring modulators. A recording head 18 records the output current of the low-pass filter 114 with a frequency range of 0 to 1500 Hz in the order ABAB on the magnetizable disk 11 coupled to the motor 9, and a recording head 28 records the output currents of the high-pass filter 125 with a frequency range of 1500 to 3000 Hz in the order BABA as shown at 11 and 21. These recordings are repeated periodically every 50 milliseconds. In this case, two scanning heads 12 and 13 are arranged on the disk 11. They are spaced 25 milliseconds apart and their output currents are controlled by relays 6 and 16. The scanning heads 22 and 23 arranged on the disk 21 also have a distance of 25 milliseconds. Their output currents are controlled by relays 26 and 36. Thus, conversations on the first and second channels can be listened to on earphones 10 and 20, respectively, by properly grouping the currents controlled by these relays. The attenuators 15, 25, 35 and 45 are adjusted so that they balance the spectrum of the speech currents with medium power density. The erase heads 19 and 29 are used to erase the recorded speech at the end of each revolution of the magnetizable disks 11 and 21 .

This improved circuit has the same transmission Right properties as the circuit "shown in the previous example, but it is this respect think of the effort, since the number of filters is reduced. It is possible for the level variations of the receiving side sound by \ ^r SE OF to reduce two readheads.

Example 3

Fig. 9 shows a block diagram of an entire multichannel telephony system for wide area traffic. The blocks with the transmitting devices are labeled Fasit-X , while those with the receiving devices are labeled Fasit-R . A and B are two sets of telephone stations that can be interconnected in accordance with the invention. C is a pair of conventionally interconnected telephone sets. An arrangement E is also provided, for example a service line or an ordinary line with a switching device for connecting the telephones C and C to one another. The notch filters for suppressing the synchronization signals are denoted by BEF , while HYB denotes a hybrid circuit and EQU denotes the corresponding simulation.

A carrier wave with a frequency of 300 Hz can be derived in O ₂ from the network with 50 or 60 Hz, and 12.5 Hz can then be obtained from the 300 Hz of the carrier current by a frequency divider marked O ₁ for synchronization. M is a modulator in which the carrier wave of 300 Hz is amplitude modulated by the output current of 12.5 Hz. This synchronization signal is sent to the line via the filter _{BPF 1.} The synchronization frequency of 12.5 Hz can be obtained at the receiver side by means of a detector D by rectifying the modulated synchronization signal, which has been filtered out by a bandpass filter BPF ₂ tuned to 300 Hz and amplified in an amplifier A ₁ . The output current of this detector is a sinusoidal alternating current with a frequency of 12.5 Hz, and its phase should be exactly matched to that in Fasit-X and that in Fasit-R. It is then reshaped into a square wave.

Synchronizing and paging devices are not part of the invention but are required for this system. The synchronization system, which consists of O ₁ , O ₂ , M, BPF ₁ , BPF ₂ , A ₁ and D , is also shown in FIG. As the carrier frequency for the synchronization signal, 300, 2700 Hz or any other frequency free from any interference can be selected for the transmission; this is modulated with the synchronization frequency of 12.5 Hz, for example. This low frequency is filtered out on the receiver side, its phase corrected, converted from sinusoidal to rectangular by means of a special deformation circuit and passed on to the relay. In the system according to the invention, the call can easily be transmitted. This is explained below using a system with two frequency bands.

Two carrier waves with frequencies of, for example, 500Hz in the first subband and 2000Hz in the second sub-band are amplitude modulated with the same ringing current with a frequency of 16 Hz. A 16 Hz signal converted in this way always works regardless of the interruptions over the line if one neglects the difference in the carrier frequency. The ringing current of 16 Hz can then be recorded on the receiver side and smoothed by a suitable low-pass filter. The telephone subscribers can therefore use their telephone system in the same way as an ordinary one Telephone. It is also possible to reverse the connections of the speaker at the far end by reversing the Replace the phase of the synchronization signal for the relay control at the near end without the transmitted synchronization signal is changed.

The longer the connecting line, the greater the advantage of the invention, since it saves on cables The saving on the frequency band is particularly evident when the invention is applied to wireless Transmissions are advantageous because the available frequency band according to the invention with better efficiency can be used.

Claims (4)

Patent claims: 1. Multi-channel telephone system for the intermittent transmission of several simultaneous messages direct over the same line, characterized that the speech streams of each channel on the transmission side in at least two sub-frequency ranges are divided and with interchanging the speech streams at the same time different subranges of different channels while maintaining their original frequency position are transmitted and that on the receiving side the speech streams of the sub-areas of each Channel composed and the resulting time gaps by repeating each immediately previously received and stored speech streams are filled in. 2. Telephone system according to claim 1, characterized in that the duration of the intermittent transmitted message sections is each V12 to V25 seconds. 3. Telephone system according to claim 1 or 2, characterized by a rotating, magnetizable Recording medium as a memory for the received message sections. 4. Telephone system with two channels according to claim 1 to 3, characterized in that on the transmitting side by periodic switching by means of relays (4 or 14), which are controlled by a square wave generator (3) with a frequency below the speech frequencies, from the speech streams of the two Channels two signals are picked out which, mutually shifted by the duration of a message section, each contain the message content of both channels intermittently and after clipping one signal by a low-pass filter (112) to the lower part of the speech frequency range and the other signal by a band-pass filter ( 122) are transmitted to the upper part of this area together via the line (5), and that on the receiving side, the two signals are separated from one another by appropriate filters (114 or 125) and transferred to two disks (11 or . 21) are recorded magnetically, from which the signals to Ausf The transmission gaps between the message sections are scanned by two magnetic heads (12, 13 or 22, 23) offset from one another in the direction of rotation of the disks and by means of relays (6, 16 or 26, 36) to the original voice streams of the two channels The motor (9) and two square wave generators (7 and 17) on the receiving side feeding the relays are controlled by a synchronizing signal transmitted from the transmitting side (Fig. 8th). Considered publications: German Patent Nos. 549 855, 728 838;
British Patent Nos. 327,709, 352 095. For this purpose 2 sheets of drawings © 009 627/297 10.