Mechanism for telephone key-pad dialler - has select bars operated by key lever following lever to set code and blocking to prevent double operation

摘要

Mechanical select linkage and interlocks are operated by the keypad dialling unit for a telephone instrument. Combinations of longitudinal select bars are operated by each key depression according to the required code to be output from the electrical switch circuitry associated. Each hinged button operates a further hinged code select bar. Each key is hinged and has a bottom extension which, when operated, pushes back against a second hinged bar carrying the select code by having various sized plates to operate one or more longitudinal select bars by engaging the select bar teeth. Each select bar operates a separate rate switch unit. To prevent misoperation, a barrier linkage is provided. The first select bars to pass through it close the segments of the barrier on two levels and against side springs to prevent subsequent operation of more keys at the same time.