ing intruding parties had secure statue to block intrusion. needs of the business. Early designs of PABX software were com- Manager-secretary facilities, which enabled call filtering by the plicated to use and relied on the system manager understanding not secretary, but with manager able to contact the secretary and only the business requirements but also how the PABX database bit automatic switch through to the manager when secretary is pattern was organised, since changes to the database involved la- absent. Voice calling by secretary or manager and possibly auto boriously entering bit patterns at the appropriate points to re-pro- answer by either if handsfree telephones are in use. One key gramme the system. This led to the development, particularly in the calling of either manager or secretary. Visual indication of US, of off line PC controlled database management systems, which either manager or secretaries' line by either one. had a more friendly user interface. This was used to program the 4. Private line working, where a special line can be directed to a new requirements off line and then up load this onto the PABX senior manager for undisturbed confidential calls. during a quiet traffic period. PABX suppliers have in the main now 5. Account coding of calls, either forced by the user on initiation developed menu driven database management software that is resi- of a call (useful in situations where consultants/partners must dent as a set of application programs in the PABX and allows online charge all clients for calls) or account coding at will, where the changes to be made to the database without the need for out of hours user can enter an account code during either an incoming or working by the system manager. The application software is the outgoing call to charge the client. most complex and handles a number of functional areas such as Broker's call, where the telephone user can hold two calls and telephone or terminal interface, incoming call disposition, outgoing shuttle between each call with sec