Abstract: A caller number notification synchronized with an incoming signal is disclosed. An analog circuit interface section outputs incoming call signal presence information that shows whether to receive the incoming call signal that has the information indicated at a predetermined position on a highway and outputs the received caller ID to a speech signal path. An analog extension interface section detects the incoming call signal presence information on the highway, detects the caller ID on the speech signal path, generates an incoming call signal based on the detected incoming signal presence information and sends out the generated incoming call signal and the detected caller ID to the analog extension. A system control section connects the analog circuit interface section to the analog extension interface section.

Abstract: An office-line trunk circuit is provided to selectively operate on ground-start and loop-start modes. In this circuit, a DC current detection circuit has (i) a first photo coupler detecting a DC loop current caused responsively to supply of the ground to a tip line and a negative power to a ring line from an office bilateral trunk and (ii) a resistor whose resistance is adjusted to prevent a loop start in the office bilateral trunk and allow DC current to be detected. The first photo coupler detects the loop current using the resistor. An incoming detection circuit has a second photo coupler detecting a ring signal coming from the office bilateral trunk. A DC sink circuit has a diode bridge placed between the tip and ring lines and configured to have a DC circuit provided with a transistor controlling the DC loop current so that the office bilateral trunk is allowed to selectively be loop-activated and loop-held.

Abstract: A caller number notification synchronized with an incoming signal is disclosed. An analog circuit interface section outputs incoming call signal presence information that shows whether to receive the incoming call signal that has the information indicated at a predetermined position on a highway and outputs the received caller ID to a speech signal path. An analog extension interface section detects the incoming call signal presence information on the highway, detects the caller ID on the speech signal path, generates an incoming call signal based on the detected incoming signal presence information and sends out the generated incoming call signal and the detected caller ID to the analog extension. A system control section connects the analog circuit interface section to the analog extension interface section.

Abstract: An office-line trunk circuit is provided to selectively operate on ground-start and loop-start modes. In this circuit, a DC current detection circuit has (i) a first photo coupler detecting a DC loop current caused responsively to supply of the ground to a tip line and a negative power to a ring line from an office bilateral trunk and (ii) a resistor whose resistance is adjusted to prevent a loop start in the office bilateral trunk and allow DC current to be detected. The first photo coupler detects the loop current using the resistor. An incoming detection circuit has a second photo coupler detecting a ring signal coming from the office bilateral trunk. A DC sink circuit has a diode bridge placed between the tip and ring lines and configured to have a DC circuit provided with a transistor controlling the DC loop current so that the office bilateral trunk is allowed to selectively be loop-activated and loop-held.