Frequency selective ringer circuit
US4653093A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 26, 1985 |
| Grant date | Mar 24, 1987 |
| Priority date | — |
| Expiry date | Jul 26, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q5/10
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A frequency selective ringer circuit which utilizes a constant current source in conjunction with an array of resistors and switches for developing a frequency selective window with which to detect an incoming frequency at the tip and ring inputs of a telephone system. The incoming frequency is doubled and converted to a d.c. level which is utilized as the converted level which is evaluated by the circuit. Where the converted voltage level falls within the established window, a drive circuit is energized for actuating a transducer such as a piezoelectric crystal or loudspeaker. Frequency selection is made by the simple expedient of closing one of a plurality of SPST switches. The circuit also may include a circuit for automatically deactivating the mechanical bell of an existing telephone set without the removal thereof.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.