1. Cellulose ethers with a specific substitution pattern, characterised in that they are substituted predominantly in the C3 position of the anhydroglucose unit of the cellulose.
2. Cellulose ethers according to claim 1, characterised in that the partial DS in the C3 position based on the total DS is 60%.
3. Cellulose ethers according to claim 1 or 2, characterised in that the partial DS in the C6 position based on the total DS is 15%.
4. Process for the preparation of cellulose ether according to claim 1 to 3 by reaction of cellulose dissolved in N-methylmorpholine-N-oxide monohydrate (NMMNO) and optionally other inert organic solvents with alkylation reagents, characterised in that the reaction takes place in the presence of an insoluble solid phase catalyst, stabilisers and optionally additional soluble co-catalysts.
5. Process according to claim 4, characterised in that the solid phase catalyst used is a basic compound which is insoluble in the reaction system. Process according to claims 4 and 5, characterised in that the solid phase catalyst has quaternary ammonium groups.
7. Process according to claims 4 to 6, characterised in that the solid phase catalyst used is an anion exchanger which is insoluble in the reaction system.
8. Process according to claims 4 to 7, characterised in that the solid phase catalyst is an insoluble polystyrene-based anion exchanger containing quaternary ammonium groups.
9. Process according to claims 4 to 8, characterised in that the etherification reaction is carried out in the presence of a co-catalyst which is soluble in the reaction system.
10. Process according to claims 4 to 9, characterised in that the co-catalyst is a quaternary ammonium base which is soluble in the system, preferably trimethylbenzylammonium hydroxide.
11. Process according to claims 4 to 10, characterised in that the co-catalyst is a soluble phase transfer catalyst, preferably a quaternary ammonium salt which is soluble in the system, particularly trimethylbenzylammonium chloride or tetrabutylammonium chloride.
12. Process according to claims 4 to 11, characterised in that etherification agents used are epoxy compounds, preferably ethylene oxide, propylene oxide, epoxypropanol.
13. Process according to claims 4 to 12, characterised in that etherification agents used are vinyl compounds, preferably acrylonitrile, methyl vinyl ketone, vinylsulfonic acid, the salts or esters thereof.
14. Process according to claims 4 to 13, characterised in that etherification agents used are halogenalkyl derivatives, preferably monochloroacetic acid, Na-monochloroacetate, methylchloride, ethylchloride, benzylchloride.
15. Process according to claims 12 to 14, characterised in that etherification is carried out with several etherification agents simultaneously or successively.
16. Process according to claims 4 to 15, characterised in that organic diluents used are dipolar aprotic solvents, preferably dimethylsulfoxide or N-methylpyrrolidone.
17. Process according to claims 4 to 15, characterised in that organic diluents used are protic media in concentrations without a coagulating effect, preferably n- or iso-propanol, n-, iso- or tert.-butanol.
18. Process according to claims 4 to 17, characterised in that the reagents are metered by way of the vapour phase, in the liquid form or dissolved in one or more of the components contained in the system.
19. Process according to claims 4 to 18, characterised in that the solid phase catalyst is used in a suspension compatible with the system, preferably in suspension in NMMNO, organic diluent or mixtures thereof.
20. Process according to claims 4 to 19, characterised in that the solid phase catalyst is brought into contact with the reaction system before, andor during andor after the reagent metering.
21. Process according to claims 4 to 20, characterised in that the reaction is carried out in a continuous process, preferably in a tubular reactor, a cascade of agitated reactors or a loop reactor.
22. Process according to claims 4 to 21, characterised in that the reaction system flows through the solid phase catalyst.
23. Process according to claim 22, characterised in that the solid phase catalyst is applied to one or more intermediate plates.
24. Process according to claims 4 to 23 characterised in that a co-catalyst is added before andor during the contact of the reaction system with the solid phase catalyst.
25. Process according to claims 4 to 24, characterised in that the etherification reaction is carried out at room temperature to 120 C., preferably from 30 to 100 C.
26. Process according to claims 4 to 25, characterised in that the reaction times are from 5 min to 24 hours, preferably from 10 min to 6 h.
27. Process according to claims 4 to 26, characterised in that the solid phase catalyst is reactivated with a base using solvent components used to dissolve cellulose.
28. Process according to claims 4 to 27, characterised in that the solid phase catalyst is reactivated with NaOH, preferably dissolved in NMMNOwaterorganic solvent.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A subscriber loop interface circuit apparatus comprising:
a signal processor having distinct sense inputs for each of a sensed tip signal and a sensed ring signal of a subscriber loop, wherein the signal processor generates a linefeed driver control signal in response to the sensed signals; and
a codec for bi-directional communication of voiceband data between the analog subscriber loop and a digital interface of the signal processor, wherein the signal processor and the codec reside within a same integrated circuit package.
2. The apparatus of claim 1 wherein the codec and the signal processor reside on a same integrated circuit die.
3. The apparatus of claim 1 further comprising:
a linefeed driver portion for driving the subscriber loop in accordance with subscriber loop control signals provided by the signal processor, the linefeed driver portion providing the sensed tip and ring signals.
4. The apparatus of claim 3 wherein each of the signal processor and the linefeed driver portion resides on an integrated circuit die.
5. The apparatus of claim 3 wherein the signal processor and the linefeed driver portion reside on separate integrated circuit die within the same integrated circuit package.
6. The apparatus of claim 3 wherein the signal processor and the linefeed driver portion reside on a same integrated circuit die.
7. The apparatus of claim 3 wherein each of the signal processor and the linefeed driver portion resides on separate integrated circuit die in separate integrated circuit packages.
8. The apparatus of claim 3 wherein the linefeed driver portion further comprises:
a tip control circuit; and
a ring control circuit, wherein the tip and ring control circuits vary tip and ring node voltages of the subscriber loop in response to the linefeed driver control signals.
9. The apparatus of claim 8 wherein the tip and ring control circuits provide d.c. isolation between the signal processor and the subscriber loop.
10. The apparatus of claim 1 wherein the signal processor is a complementary metal oxide semiconductor (CMOS) integrated circuit.
11. The apparatus of claim 1 wherein the signal processor calculates common mode and differential mode components of the subscriber loop.
12. The apparatus of claim 1 wherein the signal processor computes common mode and differential mode current and voltage components of the subscriber loop.
13. The apparatus of claim 1 wherein the signal processor operates in a positive voltage range with respect to ground to generate the linefeed driver control signals for controlling a linefeed driver operating at a negative d.c. voltage offset relative to the signal processor, wherein the offset is at least approximately 40 VDC.
14. The apparatus of claim 1 wherein the signal processor performs at least one of the subscriber loop supervisory functions of ring trip, ground key, and off-hook detection.
15. The apparatus of claim 1 wherein the signal processor further comprises a programming interface to enable programmatic control of at least one of the following parameters: battery control, battery feed state control, voiceband data amplification, voiceband data level shifting, longitudinal balance, ringing current, ring trip detection threshold, off-hook detection threshold, and audio output signal termination impedance for voiceband communication signals superimposed on the linefeed driver control signals.
16. The apparatus of claim 1 wherein the signal processor superimposes outgoing analog voiceband communications on the linefeed driver control signals.
17. The apparatus of claim 1 wherein the linefeed driver control signals include separate tip control signals and ring control signals.