Keyboard type telephone station adapted to transmit dialling pulses and multifrequency signals
US3988549A · kind A · utility
6Cited by
8References
2Claims
0Family size
Inventors
Key dates
| Filing date | Feb 10, 1975 |
| Grant date | Oct 26, 1976 |
| Priority date | — |
| Expiry date | Feb 10, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/30
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Telephone set arrangement designed to be used as a computer terminal. It has a first call generator transmitting call pulse trains and a second call generator transmitting call multifrequency signals. During the call, the two kinds of call signals are transmitted simultaneously. After completion of the call, the supply current is reversed as usual. The current reversal is detected and the pulse train generator is then blocked. Any transmission of signals after completion of the call is then made only in the form of multifrequency signals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.