Control Card The Control Card slides into the Card Frame from the right side, parallel to the wall. It plugs directly into the Power Supply unit, forming a backplane for the peripheral cards, It contains the following hardware: – Central Processing Unit (CPU), – DX switching matrix (switches voice and data), – Digital Signal Processor (tone generation, tone detection and conference circuits), – Five DTMF receivers, – Timing and control circuits, – Watchdog Timer (monitors processor sanity), – Memory Module interface, – Peripheral card interface circuits, – Attendant Console interface, – RS-232C Inter-face, – Night Bell output, – 7-segment Status display, – Status Switches. On the front edge of the Control Card, there are 3 connectors: an RS-232C port; a console port and a Night Bell. terminal block. The RS-232C port has a programmable baud rate and can be used for a printer or a recording device. The Control Card also provides a master reset switch and a 7-segment LED status display. The peripheral cards can be extracted from their 64-pin DIN connectors sufficiently to allow removal and replacement of the Control Card without removing the cables. This frees up a card slot for other cards.