The characteristics are:
a) Possibility of conversation between telephone and external line or between telephone and interphone speech unit. The two types of conversation are alternatives.
b) Prevalence of communications towards the external telephone line (default) or towards the telephone switchboard.
c) Transfer of interphone call to urban line towards a programmed number with signalling of function being performed.
d) Control of auxiliary "door opening", "gate" and "stair light on" functions during interphone conversion, during external line conversation and at rest.
Remote control of auxiliary functions through password protected procedure
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