Abstract: In a calling signal transmitting apparatus, a ring trip equipment, including a ring trip detecting circuit for detecting a ring trip signal in response to an off-hook operation of the telephone set during a signal state of an intermittent ringing signal and a loop detecting circuit for detecting a loop signal in response to an off-hook operation of the telephone set during a nonsignal state of the intermittent ringing signal. Also included are a logical OR gate circuit, for providing, as a status signal, a logical sum of the ring trip signal and the loop signal, and a supervising circuit for supervising the status signal.

Abstract: A switching system having a capability for telecommunication conferences, including therein, at least, a speech path memory, a mixing circuit, and a feedback circuit. The speech path memory is operative to store therein voice data signals provided from subscribers holding a conference. The mixing circuit is operative to mix two voice data signals. The feedback circuit is operative to feed the thus mixed voice data signals back to the speech path memory to accumulate therein each set of the mixed voice data signals for the subscriber's subscriber except each own voice data signal, whereby the subscribers receive respective accumulated voice data signals.

Abstract: A digital time-divison switch comprising a multiplexer which multiplexes digitalized voice signals, supervisory signals transmitted from line circuit portions, and so forth, and which inserts these signals into predetermined time slots. The digital switch also includes a signal-extracting circuit which extracts the supervisory signals from the time slots assigned for control signals and which transmits the extracted supervisory signals to a common control unit through the supervisory signal receiver, a switching network which switches data time slots, a signal inserting circuit for transmitting control signals to the line circuit portions, and a distributor circuit for distributing the voice signals and so on to each line circuit.

Abstract: A signal sending control system for use in a telephone system includes a ringing signal sending circuit having a signal source for generating a continuous ringing signal, interrupting means for controlling the sending of the ringing signal over each subscriber line, one switch for each subscriber line for selectively and switchably connecting the respective subscriber line to a speech network of the system and to the ringing signal sending circuit, a common controller for providing control information as to the duration of the ringing signal, and a control circuit for individually controlling the switching circuit of each subscriber line in accordance with the control information and for controlling the transmission duration of the ringing signal.