16.7. Auto Disconnect CircuitFunction:This circuit is used to detect the fact that another telephone connected to the same line is OFF-HOOK while the unit is in a receivingstatus or OGM transmitting status.Circuit Operation:The voltage DSP (DCIN1) is monitored. If a parallel-connected telephone is put into an OFF HOOK status, the presence/absenceof a parallel connection is determined when the voltage changes by 0.2V or more.When the set detects the parallel-connected telephone is OFF HOOK status, the line is disconnected.Note:DSP is IC201.16.8. Parallel Connection Detect CircuitFunction:In order to disable call waiting and stutter tone functions when using telephones connected in parallel, it is necessary to have acircuit that judges whether a telephone connected in parallel is in use or not. This circuit determines whether the telephoneconnected in parallel is on hook or off hook by detecting changes in the T/R voltage.It is like an “Auto Disconnect Circuit”.Circuit Operation:Parallel connection detection when on hook:When the set is on hook, the voltage is monitored at DSP (DCIN0). There is no parallel connection if the voltage is 2.50 V or higher,while a parallel connection is deemed to exist if the voltage is lower.Parallel connection detection when off hook:When the set is off hook, the voltage is monitored at DSP (DCIN1); the presence/absence of a parallel connection is determinedwhen the voltage changes by 0.2 V or more.55KX-TG2240BXS / KX-TGA228BXS
