Telephone answering system with ring detector

Claim 1

In a telephone answering system whihc includes, input circuit means to be coupled to a telephone line to respond to telephone messages received over the telephone line, a message magnetic tape recording means, and control circuit means responsive to a predetermined voltage level to activate the announcement magnetic tape storage means and cause a recorded announcement to be transmitted to a calling party during a first time interval (T-1), and for switching the system into a message receiving mode at the end of the first time interval to permit a message from the calling party to be recorded on the message recording tape, the combination of: ring-detecting means coupled to said input circuit means and responsive to ring signals received over the telephone line to produce a voltage pulse in response to each such ring signal; resistance-capacitive integrating means coupled to the ring-detecting means for integrating the voltage pulses produced thereby until the predetermined voltage level is reached so as to cause the announcement storage means to be activated after a first predetermined number of ring signals have been received over the telephone line; and further circuit means responsive to the first activation of the announcement storage means by the integrating means to change the capacitive value of the integrating means, so that the integrating means cuases each subsequent activation of the announcement storage means to occur after a second predetermined number of ring signals, less than said first predetermined number have been received over the telephone line.