SU811504A1 - Multifrequency receiver of key pulser dialing - Google Patents

Description

one

The invention relates to telecommunications and can be used in communications equipment to receive keypad dialing signals transmitted over two-wire subscriber telephone lines by a two-band frequency method in the talk spectrum.

A multi-frequency receiver of signals of a dial pad is known, containing a matching unit, the output of which is connected to the input of the first and second notch filters, the output of each of which is connected via a corresponding limiter to the selection, detection and processing unit of the signal frequencies, and the matching unit contains a relay for switching the buzzer signal from a group of disconnecting contacts and series-connected differential unit, frequency equalizer and operational amplifier, the output of which Is the output of the matching unit, while the control input of the differential unit is connected to one of the open contacts of the buzzer disconnection relay, one of the winding pins of which is connected to the ground bus 1.

However, the well-known multi-frequency receiver is not sufficiently high noise immunity.

The purpose of the invention is to improve noise immunity.

For this purpose, a multi-frequency receiver of signals of a dialing number, containing a matching unit, the output of which is connected to the input of the first and second notch filters, the output of each of which is connected to the allocation, detection and processing unit of the signal frequencies through the corresponding limiter, and the matching unit has a buzzer-off relay a signal with a group of break contacts and a series-connected differential unit, a frequency equalizer and an operational amplifier, the output of which is output to the matching unit, wherein the control unit of the differential input coupled to one of the normally closed relay contacts interrupting beep, a matching block administered resistors and the group of switching contacts of relays turning off the beep, the output of the differential

through the first, second and third resistors connected in series to the output of the operational amplifier, the auxiliary input of which is connected to the connection point of the second and third resistors, the fourth resistor is connected to the connection point of the first and second resistors with one of its terminals, This is the first output of the frequency equalizer through a group of closing contacts of the relay for switching off the buzzer signal is connected to the bus Earth, besides the frequency equalizer of the matching unit is designed as The solder is from a series-connected resistor and a chain of parallel-connected capacitor and inductor, the first and second outputs of the divider are respectively the input and output of the frequency equalizer, and the third output of the divider is connected to the Earth bus, moreover the frequency equalizer of the matching unit is made in the form of a divider serially connected active bandpass filter and two resistors, the first and second pins of the divider are respectively the input and output of the frequency equalizer, and the third output of the divider is connected to the Earth spike; in addition, the frequency equalizer of the matching unit consists of the first and second resistors connected in series and the active bandpass filter, whose input is connected to the connection point of the first and second resistors, the second output of the first resistor and the output of the active bandpass filter respectively, the input and output of the frequency equalizer, and the second output of the second resistor is connected to the EARTH bus.

FIG. 1 shows the structural electrical circuit of the proposed device; in fig. 2, 3, and 4 are structural block diagrams of a matching unit with different realizability of the frequency equalizer.

The multi-frequency receiver contains a matching unit 1, notch filters 2 and 3, limiters 4 and 5, and a block 6. for extracting, detecting and processing signal frequencies.

The matching unit 1 comprises a differential block 7, a breaker group, their contacts 8 and a group of closing contacts 9 of the relay for switching off the optical signal, the winding of which in FIG. 1 not shown, the first, second, third and fourth resistors 10-13, operational amplifier 14 and frequency equalizer 15.

Frequency corrector 15 (Fig. 2) contains a resistor 16, a capacitor 17, an inductance coil 18.

Frequency corrector 15 (Fig. 3) consists of an active band-pass filter 19 and resistors 20 and 21.

Frequency corrector 15 (Fig. 4) consists of two resistors 22 and 23 and an active band-pass filter 24.

The device operates as follows and during the reception of the first digit of the dialing number to the subscriber who has picked up the microtelephone handset, through the group of disconnecting contacts 8 and the differential

unit 7 from a special high-precision generator (not shown in fig. 1) a buzzer signal is produced. Answer stephists. Part of this signal, uncompensated by differential block 7, falls from its

output to the frequency equalizer 15 and the nerve resistive divider, consisting of resistors 10 and 13. For a signal acting on the non-inverting input of the operational amplifier 14, this amplifier with a second resistive divider, consisting of resistors 11 and 12, is a non-inverting amplifier with the gain determined by the expression;

TU-f ii {-f nil V niO

Kg- ---- at 13.

where Rll, 12 and / 13 are the resistances of resistors 11, 12 and 13, respectively, shown in FIG. one.

For a signal taken from the output (midpoint) of the first resistive divider, consisting of resistors 10 and 13. The operational amplifier 14 with the second resistive divider, consisting of resistors 11 and 12, in the value of negative feedback, is an inverting amplifier, whose gain is determined by the expression:

35

Taking into account the transmission coefficients KP of the frequency equalizer 15 (denoted below) of the first resistive divider, consisting of resistors 10 and 13

/ ,,

(defined by the expression

L; I and -R A, 10

You can write an expression for the signal transfer coefficients from the output of the differential block 7 along both amplification branches through an operational amplifier

14:

for the inverting branch, k,. If

- A-h AChK

for the inverting branch / („/ С-

 / (or) If the gain factors are D + and / (-, the transfer coefficients / (cc (at the frequency of its maximum) and / Xu, is chosen so that at the resonance frequency of the frequency equalizer 15, the equality Kn -Kn is true, then at the output of the operational amplifier 14, a full compensation of the signal arriving at this frequency occurs, i.e. the compensation of the buzzer signal, the response of the station. It should be noted that compensation occurs only

at zero phase shift at the output of the frequency equalizer 15. what happens at resonance is the frequency of the dependent element of frequency equalizer 15. Thus, operational amplifier 14 with a frequency equalizer and resistive dividers made with resistors 10 and 13 and 11,

12 is a notch filter tuned to the frequency of the buzzer signal Answer station. For all other sigals, the op amp, 14 is invert. with the gain, determined, on the one hand, by the first resistive divider made on the resistors 10 and

13 and, on the other hand, the second resistive divider, consisting of resistors And and 12, included in the negative circuit

feedback of the operational amplifier 14. This gain is chosen so as to ensure the normal operation of the limiters 4, 5, taking into account the attenuation of the signals of the dial pad in the subscriber line and the differential unit 7.

After the first digit of the dialing number is triggered by the relay of the buzzer disconnection, the station responds, the group of disconnecting contacts 8 of this relay is opened, the special buzzer signal generator is disconnected from the differential block 7, which stops the signal to the subscriber. At the same time, the group of closing coitacts 9 of the mentioned relay, which shunts the output of the frequency equalizer 15, closes, thereby stopping the compensation of the signal and the frequency of the buzzer. The response of the station and the operational amplifier 14 with resistive dividers with resistors 10, 13 and 11, 12 becomes an inverting amplifier also at the frequency of this signal with the gain factor indicated above. In other words, the frequency response of the L matching unit of the receiver of a tastatura dialing after receiving the first digit becomes frequency independent at the frequency of the buzzer response signal.

The work of the remaining blocks of the receiver is unchanged during the reception of all digits of the set. Signal of a two-frequency parcel from a generator of a remote telephone set. having passed through block 1, it goes to the inputs of group notch; filters 2 and 3, which suppress the frequencies of the neighboring group in their group. In each group, the signals from the outputs of the notch filters 2 and 3 are fed to the inputs of the limiters 4 and 5, which are connected by their inputs to the block 6 for the selection, detection and processing of signal frequencies. In block 6, signals from the limiters are allocated, as a rule, to bandpass

filters and then detected. The voltages obtained from the outputs of the detectors are compared in terms of the threshold with the threshold and the response of the threshold devices determines the arrival of a particular frequency. Threshold trigger signals

Signal frequency devices are processed further by comparison with the control time delay, checked for the correctness of the combinations (combinations that do not correspond to code messages, for example, one frequency in only one group or two or more frequencies in one group are excluded), are decoded and output to the station equipment in the form of potentials 16 wires, ten of which correspond to ten digits, and six are used for. transfer of official sigals.

1a of FIG. 2 shows a structural electrical circuit of the multi-frequency receiver unit 1 of the signals of the keyboard dialing, which discloses how to perform the frequency equalizer 15, performed as a frequency-dependent divider with an additional resistor 16 in the longitudinal arm and /. A contour formed by a capacitor 17 and a coil of inductance 18 in the transverse shoulder. The operation of the multi-frequency receiver of a dial pad, in which the irgmeek block 1. shown in FIG. 2, does not differ from the operation of the multi-frequency arpsmnik shown in FIG. 1. In FIG. Figure 3 shows the structural electrical circuit of the multifrequency receiver unit 1 of the keyboard in which the frequency equalizer 15 is executed as an active band-pass filter 19 with a resistive divider consisting of resistors 20 and 21 connected to its output. The input of the frequency equalizer 15 is the input of the active bandpass filter 19, and the output is the middle point of the resistive divider, consisting of niero of resistors 20 and 21. The operation of this unit 1 does not differ from the operation of unit 1 shown in FIG. one.

FIG. Figure 4 shows the structural electrical circuit of the multi-frequency receiver unit 1 of the keyboard dialing, in which the frequency equalizer 15 is designed as a resistive divider consisting of resistors 22 and 23, whose input forms the input of the frequency equalizer 15 and the middle point is connected to the input of the active band-pass filter 24 whose output is the output of frequency equalizer 15.

The use of one of the two last schemes can be made dependent on the type of active band-pass filter used. In the event that the active bandpass filter is built as an analog amplifying element with frequency feedback, we can recommend the use of a frequency equalizer circuit 15 shown in FIG. 3, because it has less drift zero and self-noise, which is explained by the presence of a resistive divider, which consists of resistors 20 and 21 at the output of the active band-pass filter 19. If the active irlos filter is built using negative-responsive elements that work well with low signal levels, it may be recommended to use frequency corrector 15 shown in the fng. 4, in which a rezhnostivny divider consisting of resistors 22 and 23 pre-attenuates the signal to the input of the frequency equalizer 15.

Applied multi-frequency receiver of a dial pad, in which instead of a wideband notch filter used in block 1 n a buzzer suppressor Response station (issued to the subscriber who picked up the handset from a station signaling-calling device (VCA) with a frequency of 425 ± 25 G) A narrowband notch filter has been used to effectively use the low-frequency part of the speech spectrum to suppress the receiver’s false alarms from speech signals. This became possible due to the use of a zoom signal for the application of a high-precision generator, the frequency deviation not exceeding ± 2 Hz. After the buzzer signal is turned off, it is no longer necessary to suppress it, which makes it possible to increase the noise immunity of the receiver of the keyboard set, by using to suppress the receiver’s false alarms from the voice signals of that part of its spectrum that was suppressed by the injector gear.

Claims (4)

1. Multi-frequency signal dialing signals containing the unit is matched, the output of which is connected to the input of the first and second notch filters, the output of each of which, via a corresponding limiter, is connected to the block for selecting, detecting and processing signal frequencies, and the matched unit contains a relay for switching off the buzzer signal with a group of disconnecting contacts and after constants connected to the differential block, the frequency equalizer on the operating unit, the output of which is the output of the matching block, and the control input of the differential block is connected to one of the disconnecting contacts of the disconnection signal of the digital signal, characterized in that, in order to improve noise immunity, matching unit entered resistors n the group of NC closure contacts of the relay for switching off the buzzer signal, the output of the differential unit through the first, second and third resistors connected in series with the output an operational amplifier, the additional input of which is connected to the point of connection of the second and third resistors, the fourth resistor is connected to the connection point of the first and second resistors with one of its outputs, and the second to the Earth bus, this is the nerve output of the frequency equalizer through the ground of the relay contact contacts 1G the buzzer off is connected to the earth bus. 2. The signal receiver according to claim 1, characterized in that the frequency corrector of the block is matched in the form of a divider from series-connected resistors and a chain of parallel-connected capacitors and inductors, and the first and second outputs of the divider are respectively the input and 1 output of the frequency equalizer , and the third output of the divider is connected to the Earth bus. 3. Receiver signals lo n. 1, it differs by the second and the fact that the frequency equalizer of the block is coordinated in the form of a divider made of series-connected an active bandpass filter and two resistors, the first and second pins of the divider are respectively the input and output of the frequency equalizer, and the third output of the divider is connected to the bus Land 4. Receiver signals on n. I, characterized in that the frequency corrector of the block matched consists of serially connected first n second resistors and an active bandpass filter, whose input is connected to the junction point of the first n second resistors, with the second output of the first resistor h The output of the active bandpass filter is the input and output of the frequency equalizer, respectively, and the second output of the second resistor is connected to the ground bus. Sources of information, irin ing into account during the examination 1. US patent No. 3710031, cl. 179-84, 1973 (prototype). Jj -i tz cS J