Microchip TechnologyСША

HT19LG is an electronic line switch circuit that replaces the mechanical hook switch contact or a discrete hook switch in a telephone handset or modem. It switches the positive side of the telephone line using control inputs that are referenced to the negative side of the line. In its off state, it can withstand 350V on the positive input. In its on state, it has a maximum series resistance of 18?. The device provides current limiting determined by an external resistor. There are three control inputs. The HKS pin turns on the hook switch when connected to the TPG pin. This can be accomplished by using a mechanical switch which closes when the handset is physically off-hook. The LS pin allows a logic signal to turn on the hook switch. The dial pulse, Pin 6, is used to turn the hook switch off for pulse dialing. The dial pulse (DP) is active low.