CA1098631A - Ringing signal generator for use in a subscriber's connecting circuit - Google Patents
Ringing signal generator for use in a subscriber's connecting circuitInfo
- Publication number
- CA1098631A CA1098631A CA298,320A CA298320A CA1098631A CA 1098631 A CA1098631 A CA 1098631A CA 298320 A CA298320 A CA 298320A CA 1098631 A CA1098631 A CA 1098631A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- ringing
- signal generator
- pulse code
- subscriber
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Devices For Supply Of Signal Current (AREA)
Abstract
ABSTRACT:
Ringing signal generator for generating a ring-ing current in a subscriber's connecting element and comprising a line current inverter. This inverter is controlled by means of a signal having two levels obtained by encoding a sinusoidal ringing signal by means of delta modulation at a sampling frequency which considerably exceeds the frequency of the ringing current. Use: elec-tronic devices in telephone exchanges.
Ringing signal generator for generating a ring-ing current in a subscriber's connecting element and comprising a line current inverter. This inverter is controlled by means of a signal having two levels obtained by encoding a sinusoidal ringing signal by means of delta modulation at a sampling frequency which considerably exceeds the frequency of the ringing current. Use: elec-tronic devices in telephone exchanges.
Description
Pl-l~ 77 ~l7 GL/W~/~Jor~g 24.11.l977 Ringing signal generator for use in a subscriber's connecting circuit.
The invention relates to a ringing signal generator for use in a subscriber's connecting circuit, comprising Q
device provided with a control inp1lt for reversing the supply current in the subscriber's line.
It is known that subscriber~s conn0cting circui-ts which enable the generation or d0tection of signals exchanged over a subscriber's loop (transmitting the ringing signal, direct current supply of the subscriber's line, re~ersing this direct current) are generally us0d in electronic switching and concentration apparatus in telephone exchanges.
In said subscriber's connecting circuits the generation of the ringing signal (sinusoidal signal with a frequency of 5O Hz at an r.m.s. voltage of approximat0ly 75 volts) often gives rise to problems for a practical implementation.
Reversing the line current was already used for generating ringing signals, having a ~requency of 5O Hz, and that-by means of an inverter controlled by means of square-wa~e signals having said frequency of 5O Hz. The problem arises then that in the line all odd harmonics of the frequency of 5O Hz are produc0d with a high le~el, which can result in an impermissible crosstalk in the adjacent subscriberls line. In addition, the administratlons impose r0lative:Ly strlct standar~ds as regards the l0vel~0f~the harmonics of th0 ringlng current and said standards excLude the~practical applicability of said technique.
The invention relates to a ringing signal generator for use in a subscriber's connecting circuit, comprising Q
device provided with a control inp1lt for reversing the supply current in the subscriber's line.
It is known that subscriber~s conn0cting circui-ts which enable the generation or d0tection of signals exchanged over a subscriber's loop (transmitting the ringing signal, direct current supply of the subscriber's line, re~ersing this direct current) are generally us0d in electronic switching and concentration apparatus in telephone exchanges.
In said subscriber's connecting circuits the generation of the ringing signal (sinusoidal signal with a frequency of 5O Hz at an r.m.s. voltage of approximat0ly 75 volts) often gives rise to problems for a practical implementation.
Reversing the line current was already used for generating ringing signals, having a ~requency of 5O Hz, and that-by means of an inverter controlled by means of square-wa~e signals having said frequency of 5O Hz. The problem arises then that in the line all odd harmonics of the frequency of 5O Hz are produc0d with a high le~el, which can result in an impermissible crosstalk in the adjacent subscriberls line. In addition, the administratlons impose r0lative:Ly strlct standar~ds as regards the l0vel~0f~the harmonics of th0 ringlng current and said standards excLude the~practical applicability of said technique.
2-~ 3~ PHF 77-517 It is an object of the invention to generate ring-ing signals by means of a completely new manner of control-ling the line current inverter with a very low level of disturbing harmonics.
In accordance with the invention the ringing signal generator is therefore characterized in that said signal convertor being provided with a bivalent signal generator for the generation of a bival~nt signal obtained by coding a sinusoidal ringing signal in such a way that this bivalent signal can be demodulated by means of a filter comprising a series inductance and a parallel capacitance whereby said bivalent signal having a frequency which considerably exceeds the frequency of said ringing signal and being applied to said control input.
The invention will be further explained with refer-ence to a drawing in which Fig. 1 shows a simplified dlagram of an embodiment of the ringing signal generator, according to the invention, Fig. 2 shbws a further circuit diagram of an embodiment of said ringing signal generator.
The generator according to the invention, shown in Fig. 1, comprises a device, for reversing the supply current in the subscriber's line comprising four switches 1, 2, 3, 4. The series arrangements of the switches 1 and 2 and of the switches 3 and 4 are connected in paralleI be-tween the negative terminal S of a supply source and one side of an inductance 7 the other sid~ of which is connected to the positive termina] 6 of the supply source. The junctions of the switches~l, 2 on the one hand and 3, ~ on the other hand are connected to~terminals 8, 9 : ' , - : - . . . . .
P~-[F 77-5l7 24.11.1977
In accordance with the invention the ringing signal generator is therefore characterized in that said signal convertor being provided with a bivalent signal generator for the generation of a bival~nt signal obtained by coding a sinusoidal ringing signal in such a way that this bivalent signal can be demodulated by means of a filter comprising a series inductance and a parallel capacitance whereby said bivalent signal having a frequency which considerably exceeds the frequency of said ringing signal and being applied to said control input.
The invention will be further explained with refer-ence to a drawing in which Fig. 1 shows a simplified dlagram of an embodiment of the ringing signal generator, according to the invention, Fig. 2 shbws a further circuit diagram of an embodiment of said ringing signal generator.
The generator according to the invention, shown in Fig. 1, comprises a device, for reversing the supply current in the subscriber's line comprising four switches 1, 2, 3, 4. The series arrangements of the switches 1 and 2 and of the switches 3 and 4 are connected in paralleI be-tween the negative terminal S of a supply source and one side of an inductance 7 the other sid~ of which is connected to the positive termina] 6 of the supply source. The junctions of the switches~l, 2 on the one hand and 3, ~ on the other hand are connected to~terminals 8, 9 : ' , - : - . . . . .
P~-[F 77-5l7 24.11.1977
3~
;
via two primary windings 10, 11 of a line tr~nsformer 12, said windings having the same winding sense. The subscriber's ' loop is connected to the terminals 8 and ~. At the other end I of the line, not shown in the figures, there is the subscriber's set9 which comprises a ringing device the impedance of which is connected between the terminals of the subscriber~s line when the receiver of the subscriber's set is on the hook.
The speech signals which are supplied to the -terminals 8 and 9 are taken from the ends l4, 15 of the secondary winding 13 of said transformer 12 and inverted, said ends 14, 15 being connected to a transmission path, not shown, in a telephone exchange.
The switches of the inverter are controlled so by means of a two~level signal S, that either the switches 1, 4 ; 15 are closed simultaneously and the switches 2, 3 opened, or the switches 2, 3 are simultaneously closed and the switches 1, 4 opened. This action is obtained by controlling the switches 1 and 4 by means of the signal S and controlling the switches 2, 3 by means of the complementary signal S. It is obvious that, depending on the value of the signal S, the ourrent in the subscriber's set, connected between terminals 8, 9, flows in a first direction or in a direction opposite ; thereto. As described above, a known method for generating ringing signals with a ~requency of 50 Hz consists in that a signal having a frequency of 50 Hz is used as control signal S~for the swit~ohes. Then, however, the above-mentioned draw-backs occur, which are caused by the high level of the odd harmonics of the 50 Hz frequency.
Because of` the invention it is possible to obviate : ~ :
Pll~` 77-5l7 2l1.11.1977 i3~
said drawback by using a bivalent signal S for controlling the switches, which signal represents a modulated sinusoidal ringing signal having a frequency of 50 Hz ancl a sarnpling frequency which considerably e~ceeds 50 Hz. In Fig. 1 the signal S is generated by rneans of a bivalent signal generator 16 e.g. an analog to bivalent signal convertor. Such a convertor can e.g~ be any prior art delta modulator ~r sigma delta modulator or a pulse-width modulator etc. A sinusoidal signal having a frequency of 50 Hz and applied to the input 17 is converted in e.g. the delta rnodulator 16 into said signa] S
by means of a sampling frequency F which is determined by l the clock signal generator 18. The complementary signal S
is obtained by means of the inverter 1g. The signal S is a square-wave signal and has transitions whose instants are determined by the delta modulation and which can occur at time intervals which are a multiple of the cycle T `- ~ .
If the switches are controlled via the control input 24 by the signal S thus-formed, it was ascertained at a sampli~g frequency F which is large relative to the 50 ~z frequency of the ringing signal ~for example P = 15 kHz), that at the terminals of the ringing device of the subscriber's set, located at the other end of the line, a slgnal having a frequency of 50 Hz is obtained which is attenuated to a very small degree only whereas all the higher harmonics of this signal, which are the result of the ~ntrol of the switc~es, - are markedly attenuated by a filter comprising the sinus inductanoe 7 and by the parallel line capaci-tance which in practioe are connected in parallel with the impedance of the ringing device.
~5 ~:; - : ' -7^-~l7 ~/l.11.1977 3~
Compared with the ~lown ringing signal ~nerator control, in whlch the switches are controlled by square-wave signals of a frequellcy of 50 Hz and in which co~lparatively much energy is distributed over all the odd harmonics of said 50 hz frequency, the use of e.g. the delta modula-tion for performing said control enables the distribution of the noise spectrum which is superimposed on the signal of 50 Hz frequency over a much wider frequency band, so that the noise spectrum is filtered by the inductance 7 and the line capacitance.
~inally it was ascertained that the resulting residual voltage of the 50 Hz signai superimposed on the filtered noise spectrum and induced in the secondary winding 13 at the ends 14, 15 o-f` this secondary winding 13 is but weakly present; said residual voltage can, however, be limited by a limiter connected to said terminals 14, 15.
- It is obvious that the control signal S, obtained by means of e.g. the delta modulator from a sinusoidal signal, need not of necessity be generated in this manner. Said signal S can also be obtained by other means. It is, for example 9 possible to use a store in which the signal S is stored, for example a ROM or a circulating store, in wh~Ch the binary elements derived from e,g. the delta encoding o~
the sinusoidal ringing signal are stor~d in a cycle or half a cycle of said sinusoidal signal. So far the starting point was a ringing signal frequency of 50 ~Iz~ It is, however, obvious that the device according to the invention can be used fpr generating ringing signals of other frequencies, for xample of 25 H~.
.
.:
PIIF 77-5l7 2~ 9-;'7 ;3~
The swi-tches 1, 2, 3 and l~ of the line current inverter can be implemented by means of semiconductor circuits.
It is, for example, possible to use the device shown in ~ig. 2, in which elements corresponding wi-th the e~ements of ~ig. 1 have been given the same reference numerals. The switch 1 (or 3) is implemented by means of two transistors T1 7 T2 (or T3, Tl~) which are connected in known manner in sucll a way that they constitu-te a high-gain complex transistor. The mairl current path of the transistor Tl (or T3) is prov~d between the inductance 7 and the winding lO (or 11 ) . The base electrode of the transistor T2 (or TL~) is connected to the posi-tive terminal 6 of the battery via the resistor 20 (or 21). The switch 1 (or 3) is connected to the switch 2 (or 4) via the separating diode 22 (or 23), which is also connected to the base electrode of the transistor T2 (or T4). The switch 2 (or 4) is implemented by means of a transistor T5 (or T6), - the main current path of which is provided between the diode 22 - (or 23) and the negative terminal 5 of the battery. The base electrode of the transistor T~ is controlled by the signal S, whereas the base electrode of the transistor T6 is controlled by the signal S, these signals S and S being, for example, generated in the above-described manner and applied, after having been brought to a suitable d.c~ voltage level 7 to the transistors in order to enable control of the transistors in 23 the cut-off or saturation range. This circuit cJ~rly shows that when signal S has a value which adjuste the transistor T5 of the switch 2 to the saturation state, the two transistors T1, T2 of the swi~ch 1 are blocked by the diode 22, whereas simultaneously the transistor T6 of s~itch ~ i5 cut-off and the~ transistors T3, T4 of switch 3 are conductive, so that the P11:F 77--51i 21~.11.1977 63~
i line current can flow from termi.nal 9 to terminal 8. If the transistor T6 is adjusted to the saturation state by the signal S the action of the switches 1 and 2 is replaced by ~1 . that of the switches 3 and 4 and -the line current flows~ from terminal 8, to terminal 9.
:
: : ' . : , .
:: :
,, : , '
;
via two primary windings 10, 11 of a line tr~nsformer 12, said windings having the same winding sense. The subscriber's ' loop is connected to the terminals 8 and ~. At the other end I of the line, not shown in the figures, there is the subscriber's set9 which comprises a ringing device the impedance of which is connected between the terminals of the subscriber~s line when the receiver of the subscriber's set is on the hook.
The speech signals which are supplied to the -terminals 8 and 9 are taken from the ends l4, 15 of the secondary winding 13 of said transformer 12 and inverted, said ends 14, 15 being connected to a transmission path, not shown, in a telephone exchange.
The switches of the inverter are controlled so by means of a two~level signal S, that either the switches 1, 4 ; 15 are closed simultaneously and the switches 2, 3 opened, or the switches 2, 3 are simultaneously closed and the switches 1, 4 opened. This action is obtained by controlling the switches 1 and 4 by means of the signal S and controlling the switches 2, 3 by means of the complementary signal S. It is obvious that, depending on the value of the signal S, the ourrent in the subscriber's set, connected between terminals 8, 9, flows in a first direction or in a direction opposite ; thereto. As described above, a known method for generating ringing signals with a ~requency of 50 Hz consists in that a signal having a frequency of 50 Hz is used as control signal S~for the swit~ohes. Then, however, the above-mentioned draw-backs occur, which are caused by the high level of the odd harmonics of the 50 Hz frequency.
Because of` the invention it is possible to obviate : ~ :
Pll~` 77-5l7 2l1.11.1977 i3~
said drawback by using a bivalent signal S for controlling the switches, which signal represents a modulated sinusoidal ringing signal having a frequency of 50 Hz ancl a sarnpling frequency which considerably e~ceeds 50 Hz. In Fig. 1 the signal S is generated by rneans of a bivalent signal generator 16 e.g. an analog to bivalent signal convertor. Such a convertor can e.g~ be any prior art delta modulator ~r sigma delta modulator or a pulse-width modulator etc. A sinusoidal signal having a frequency of 50 Hz and applied to the input 17 is converted in e.g. the delta rnodulator 16 into said signa] S
by means of a sampling frequency F which is determined by l the clock signal generator 18. The complementary signal S
is obtained by means of the inverter 1g. The signal S is a square-wave signal and has transitions whose instants are determined by the delta modulation and which can occur at time intervals which are a multiple of the cycle T `- ~ .
If the switches are controlled via the control input 24 by the signal S thus-formed, it was ascertained at a sampli~g frequency F which is large relative to the 50 ~z frequency of the ringing signal ~for example P = 15 kHz), that at the terminals of the ringing device of the subscriber's set, located at the other end of the line, a slgnal having a frequency of 50 Hz is obtained which is attenuated to a very small degree only whereas all the higher harmonics of this signal, which are the result of the ~ntrol of the switc~es, - are markedly attenuated by a filter comprising the sinus inductanoe 7 and by the parallel line capaci-tance which in practioe are connected in parallel with the impedance of the ringing device.
~5 ~:; - : ' -7^-~l7 ~/l.11.1977 3~
Compared with the ~lown ringing signal ~nerator control, in whlch the switches are controlled by square-wave signals of a frequellcy of 50 Hz and in which co~lparatively much energy is distributed over all the odd harmonics of said 50 hz frequency, the use of e.g. the delta modula-tion for performing said control enables the distribution of the noise spectrum which is superimposed on the signal of 50 Hz frequency over a much wider frequency band, so that the noise spectrum is filtered by the inductance 7 and the line capacitance.
~inally it was ascertained that the resulting residual voltage of the 50 Hz signai superimposed on the filtered noise spectrum and induced in the secondary winding 13 at the ends 14, 15 o-f` this secondary winding 13 is but weakly present; said residual voltage can, however, be limited by a limiter connected to said terminals 14, 15.
- It is obvious that the control signal S, obtained by means of e.g. the delta modulator from a sinusoidal signal, need not of necessity be generated in this manner. Said signal S can also be obtained by other means. It is, for example 9 possible to use a store in which the signal S is stored, for example a ROM or a circulating store, in wh~Ch the binary elements derived from e,g. the delta encoding o~
the sinusoidal ringing signal are stor~d in a cycle or half a cycle of said sinusoidal signal. So far the starting point was a ringing signal frequency of 50 ~Iz~ It is, however, obvious that the device according to the invention can be used fpr generating ringing signals of other frequencies, for xample of 25 H~.
.
.:
PIIF 77-5l7 2~ 9-;'7 ;3~
The swi-tches 1, 2, 3 and l~ of the line current inverter can be implemented by means of semiconductor circuits.
It is, for example, possible to use the device shown in ~ig. 2, in which elements corresponding wi-th the e~ements of ~ig. 1 have been given the same reference numerals. The switch 1 (or 3) is implemented by means of two transistors T1 7 T2 (or T3, Tl~) which are connected in known manner in sucll a way that they constitu-te a high-gain complex transistor. The mairl current path of the transistor Tl (or T3) is prov~d between the inductance 7 and the winding lO (or 11 ) . The base electrode of the transistor T2 (or TL~) is connected to the posi-tive terminal 6 of the battery via the resistor 20 (or 21). The switch 1 (or 3) is connected to the switch 2 (or 4) via the separating diode 22 (or 23), which is also connected to the base electrode of the transistor T2 (or T4). The switch 2 (or 4) is implemented by means of a transistor T5 (or T6), - the main current path of which is provided between the diode 22 - (or 23) and the negative terminal 5 of the battery. The base electrode of the transistor T~ is controlled by the signal S, whereas the base electrode of the transistor T6 is controlled by the signal S, these signals S and S being, for example, generated in the above-described manner and applied, after having been brought to a suitable d.c~ voltage level 7 to the transistors in order to enable control of the transistors in 23 the cut-off or saturation range. This circuit cJ~rly shows that when signal S has a value which adjuste the transistor T5 of the switch 2 to the saturation state, the two transistors T1, T2 of the swi~ch 1 are blocked by the diode 22, whereas simultaneously the transistor T6 of s~itch ~ i5 cut-off and the~ transistors T3, T4 of switch 3 are conductive, so that the P11:F 77--51i 21~.11.1977 63~
i line current can flow from termi.nal 9 to terminal 8. If the transistor T6 is adjusted to the saturation state by the signal S the action of the switches 1 and 2 is replaced by ~1 . that of the switches 3 and 4 and -the line current flows~ from terminal 8, to terminal 9.
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Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A ringing signal generator for use in a sub-scriber's line comprising pulse code signal generator means for providing a pulse code modulated signal corres-ponding to a sinusoidal ringing signal of a given frequency and having transitions at time intervals that are a multiple of the inverse of a sampling frequency that is substantially higher than said given frequency, switch means responsive to said pulse code modulated signal for reversing a supply current to said subscriber's line during transitions of said pulse code signal, and filter means comprising an inductance in series with said switch means for substantially attenuating those frequencies of the reversed supply current in the subscriber's line that are higher than said ringing signal frequency.
2. A ringing signal generator as claimed in claim 1 wherein said pulse code signal generator comprises an analog to pulse code signal convertor having applied thereto a sinusoidal ringing signal for producing said pulse code modulated signal.
3. A ringing signal generator as claimed in claim 2 wherein said analog to pulse code signal convertor comprises a delta modulator for converting said sinusoidal signal into a delta modulated signal.
4. A ringing signal generator as claimed in claim 1 wherein said ringing signal generator comprises a memory for storing said pulse code modulated signal.
5. A subscriber's connecting element, characterized in that it comprises the ringing signal generator as claimed in claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA298,320A CA1098631A (en) | 1978-03-02 | 1978-03-02 | Ringing signal generator for use in a subscriber's connecting circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA298,320A CA1098631A (en) | 1978-03-02 | 1978-03-02 | Ringing signal generator for use in a subscriber's connecting circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1098631A true CA1098631A (en) | 1981-03-31 |
Family
ID=4110922
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA298,320A Expired CA1098631A (en) | 1978-03-02 | 1978-03-02 | Ringing signal generator for use in a subscriber's connecting circuit |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1098631A (en) |
-
1978
- 1978-03-02 CA CA298,320A patent/CA1098631A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |