| 摘要 |
PURPOSE:To reduce the power consumption at off-hook, to eliminate the need for an expensive relay and to reduce cost by using a relay contact for constant current changeover of a constant current electronic letter coil depending on a signal sent to an exchange. CONSTITUTION:The constant current processing electronic letter coil 21 makes a current flowing to an exchange 36 constant when an off-hook signal is sent, the constant current value flowing to the exchange 36 when a dial pulse signal is sent is switched from a constant current value at off-hool signal transmission depending on the difference from the resistance voltage division and a relay contact 28 disconnecting a capacitor 27 being a cause to dial distortion and a photocoupler 30 controlling on/off of the constant current circuit are provided. When a ring trip signal is sent, the ring contact 28 is closed and the constant current of the constant current electronic letter coil 21 is kept to the same value as that of the dial pulse transmission. Thus, the power consumption at hook-off is reduced and the dial pulse signal is sent without using any expensive relay to reduce the cost. |
