Internal telephone network with paired phones - automatically redirects call to second handset of pair when first is engaged

摘要

The internal telephone network employs a number of hand-sets (E1, En) which are coupled to a common multi-wire address line (AL) and arranged in pairs (E1a, E1b) allocated complementary, binary coded, address code words. The address line (AL) has a number of transmission wires which exceeds the number of binary characters of such address word. Each addressed handset (e.g. Eia) delivers a return signal (RS) to a central installation (Z), responding to the latter to direct further calls to the other handset (E1b) of the sampe pair.