Apparatus for enhancing the use of electromechanical key telephone systems

Apparatus for use with a telephone system having a plurality of stations each of which becomes active when the station goes off-hook and one of a plurality of keys at the station is actuated for selecting one of a plurality of outside central office (CO) lines connected to the stations through a key service unit (KSU), said apparatus comprising:

• (a) a station control unit (SCU) associated with each station for connecting the same to the KSU;
• (b) a main control unit (MCU) for connection between the KSU and the outside CO lines, said MCU having a computer-based central control, and a multistate line control unit (LCU) operatively associated with each outside CO line for connecting each station in parallel to the selected CO line and/or to the central control in accordance with the state of the LCU operatively associated with the selected CO line;
• and
• (c) means for effecting addressing between the MCU and the SCU's and for controlling the state of the LCU's as a consequence of such addressing when the MCU is operative such that the MCU manages connections of the system to the CO lines and signalling between the stations according to a predetermined plan contained in the control unit.

A line control unit (LCU) for connecting the tip and ring wires of an outside central office (CO) line to the inside tip and ring wires at the CO side of a key service unit (KSU) of an electrical mechanical key telehone system, said LCU comprising:

• (a) a ring detector circuit connected across the outside tip and ring wires for detecting an incoming call thereon;
• (b) a selectively adjustable signal path for connecting the outside tip and ring wires to the inside tip and ring wires;
• (c) a selectively operable internal-external switch in said signal path;
• and
• (d) means for selectively opening and closing said internal-external switch independently of detection of an incoming call by said ring detector circuit.

Apparatus for use with a telephone system having a plurality of outside central office (CO) lines comprising:

• (a) a main control unit (MCU) that includes a line control unit (LCU) associated with each outside CO line for interconnecting the same to a respective one of a plurality of inside CO lines, the state of an LCU establishing the nature of the connection between the asociated outside CO line and the inside CO line interconnected thereto;
• (b) a plurality of telephone stations each having a plurality of individually actuatable line selector keys respectively associated with said plurality of inside CO lines;
• (c) a key service unit (KSU) connected to said inside CO lines and having a cable associated with each telephone station, each cable having a conductor connected to one of the inside CO lines whereby each inside CO line is physically present in the cable;
• (d) a station control unit (SCU) associated with each telephone station for connecting the latter to different ones of said cables, each SCU being constructed an arranged to generate an address signal in response to actuation of one of the selector keys of the telephone station with which the SCU is associated;
• and
• (e) said MCU being constructed and arranged to receive address signals from the SCU's which are transmitted via the conductors in said cables.