Teleprinter private branch exchange

A teleprinter private branch exchange in which a central unit controls the traffic between the individual teleprinter terminals and, where appropriate, with at least one data line, comprising:

• a communications unit for connection to a plurality of communications terminals;
• a central unit for controlling traffic;
• a storage unit;
• a plurality of identically constructed processing units each in a respective communications unit, central unit and storage unit;
• a common bus connecting said processing units;
• said processing unit of said central unit operable to control said processing units of said storage and communications units for signal transmission one at a time;
• said processing unit of said central unit operable to trigger the execution of procedures to be executed in said central unit;
• and
• said processing unit of said central unit operable to supply addresses to said storage unit for storage areas thereof in which signals are stored or are to be stored, and wherein
• said processing unit of said communications unit includes means operable to monitor the communications terminals for the appearance of call signals and responsive to a call signal to transmit a request signal over said bus to said central unit,
• said central unit comprising means for transmitting over said bus to said storage unit addresses of signals stored in said storage unit for secure storage, and
• said central unit comprising a control system connected to said bus, a plurality of program memories connected to said control system, and said control system being operable to access said program memories in response to signals from said communications and storage units to access a desired program to be carried out.