Abstract: A digital data communications system, comprises a master station and a plurality of slave stations communicating with said master station in a multiburst scheme over a digital link having a plurality of communication channels associated respectively with said slave stations. In each frame the master station transmits a master burst over all the channels and the slave stations transmit slave bursts over the respective channels associated therewith.

Abstract: A telephone system automatic ringing code decoder useful to provide single party ringing on a multi-party telephone line. The decoder counts the number of ring bursts and detects the length of the last ring burst in the first ring burst code sequence and compares it with a preselected code. Upon finding a match, it provides an output on an SEL lead, indicating that further ringing can be applied to a subscriber's set ringer.

Abstract: A station set interface circuit for connection to a multi-party line, for prohibiting connection of a party line subscriber's set to the party line in the event the line is in use and for returning busy tone to the subscriber's set. A hookswitch flash by the subscriber causes the circuit to connect the subscriber's set to the party line for a predetermined period, while applying a warning tone to the party line for transmission to the parties of the call in progress at the beginning and end of the period.

Abstract: A circuit for efficiently applying tones or other signals to a line circuit which has a variety of conditions such as being split from the central office, and having a telephone set connected thereto either on hook or off hook. The invention is comprised of a tip lead and a ring lead having one end for connection to a central office and another end for connection to a subscriber's telephone set. A low impedance signal source including line current conducting means is connected in series with the tip or ring lead. A switchable resistance is provided for connecting a circuit path between the tip and ring leads at the telephone set end of the tip and ring lead. Preferably the low impedance signal source including the line current conducting means has a resistance which is 25% or less than the off hook impedance of the telephone set.