Electrical blocking device for telephone subscriber's appts. - has polarity reversing component allowing outgoing call connections to be blocked electrically while still allowing incoming call connections

摘要

Appts. (1) has a line input and output to, e.g. a telephone or other telecommunication terminal (T). Between its input and output, the appts. has a polarity reversal component (VS), a lock switch (SS) and a cell detecting setting (S) and resetting (RS) switch. When the lock switch (SS) is closed (position N) the appts. (1) is made transparent so that the terminal (T) can be used for incoming and outgoing calls. When the lock switch (SS) is open (position S) outgoing connections are blocked but incoming connections are not. The appts. (1) is bilingual for multi-frequency and pulsed dialling. A call suppressor (WU) is integrated in the appts. (1). When the switch (SS) is locked (position S), dial numbers (MFV or IWV) from the telephone (T) are suppressed and the dial tone can be heard by the user at the telephone, while the suppressor (WU) is by-passed by incoming calls. ADVANTAGE - User hears dial tone when outgoing calls are blocked so he realises that line is not dead.