H04Q 5/08
Signalling by continuous ac
Official title: Signalling by continuous AC
H04Q5/08 (Signalling by continuous ac) appears on 6 US grants and 0 published applications in this corpus.
Search patents in H04Q- Granted patents
- 6
- Published applications
- 0
- Assignees
- 4
- Inventors
- 8
- Latest grant
- 21 Sep 1993
Filings by year
| Year | Granted patents | Published applications |
|---|---|---|
| 1979 | 1 | 0 |
| 1980 | 0 | 0 |
| 1981 | 1 | 0 |
| 1982 | 0 | 0 |
| 1983 | 0 | 0 |
| 1984 | 0 | 0 |
| 1985 | 0 | 0 |
| 1986 | 0 | 0 |
| 1987 | 1 | 0 |
| 1988 | 0 | 0 |
| 1989 | 0 | 0 |
| 1990 | 1 | 0 |
| 1991 | 0 | 0 |
| 1992 | 1 | 0 |
| 1993 | 1 | 0 |
By publication year. Applications have been published since 2001.
Subgroups
Granted patents
Recent patents
- Telephone answering system and apparatus for direct caller selection of a party line extension21 Sep 1993US 5,247,570 AProduct Engineering & Manufacturing, Inc.
- Telephone answering system and apparatus for direct caller selection of a party line extension4 Feb 1992US 5,086,458 AProduct Engineering & Manufacturing, Inc.
- Frequency responsive selective ringing circuit25 Sep 1990US 4,959,853 A
- Frequency selective ringer circuit24 Mar 1987US 4,653,093 AFloyd Bell Associates, Inc.
- Ringing signal generator4 Aug 1981US 4,282,410 AGTE Automatic Electric Labs Inc.
No published applications in this class yet.
Most cited
By later US patents
- Telephone answering system and apparatus for direct caller selection of a party line extension33US 5,086,458 AProduct Engineering & Manufacturing, Inc. · 1992
- Party intercept in selective multifrequency ringing systems16US 4,154,987 ACircom, Inc. · 1979
- Ringing signal generator13US 4,282,410 AGTE Automatic Electric Labs Inc. · 1981
- Frequency responsive selective ringing circuit5US 4,959,853 A1990
- Telephone answering system and apparatus for direct caller selection of a party line extension4US 5,247,570 AProduct Engineering & Manufacturing, Inc. · 1993