Circuit arrangement for telephone subscriber stations with a microprocessor

摘要

The test current supplied from the exchange during the connection of a subscriber station to a line concentrator device, which lies below the power consumption of a microprocessor, is intended not yet to initiate switching processes in the station itself, since these switching processes must only take effect when the subscriber concerned has replaced his handset and normal feed current is applied to the telephone wires. This is ensured by connecting a threshold value component upstream of the microprocessor which monitors both the replacement of the handset on the station concerned and also the provision of an adequate operating voltage for the microprocessor. Only when both conditions are satisfied is the microprocessor activated and able to control the necessary switching processes in the station.