| 摘要 |
A subscriber apparatus having working ringer generators and a standby ringer generator which is alternately used when there is a fault, wherein provision is made of a traffic monitoring unit which continuously monitors the traffic of calls terminating at the subscriber lines and a ringer switching unit which switches a working ringer generator to a standby ringer generator when it is judged that the number of the terminating calls exceeds an allowable number, whereby the apparent capacity of the working ringer generators is increased. |
