Ring Communications CB901EX - Manual (Page 6)

CB901EX Operations Manual March 2011
The CB901EX printed circuit cards, are briefly described in the following:
PROCESSOR CARD
This card contains the microprocessor (MC 68HC11 series), its program and memory.
The 32K bytes program, which controls all computer operations is located in FLASH Memory).
It contains the main oscillator (10.7 MHz) and provides all timing signals in the central unit. In this
way the system is synchronized all the way through, which minimizes noise generation on the audio
links. This card also sets up/disconnects links, directed by the processor. It handles the PAM (Pulse
Amplitude Modulation) sampling control for all links. There are 32 time-slots in the system. One time-
slot is allocated by the subscriber scanner and one for the tone receiver, leaving 30 time-slots for audio
connections. This means that there is room for 15 simultaneous audio links.
AUDIO CONTROL CARD
The duplex voice control circuits are located on this card, together with the receiver and tone
transmitter. The processor fully controls the tone receiver/transmitter.
The duplex control circuit operates individually for each time-slot, which is much faster than the
processor can manage. Therefore, a separate control system is included on this card.
LINK CARD (2 cards)
It connects the audio signals between the subscribers. Each card handles 8 links and there are
always 2 link cards in the central unit.
POWER CARD
It contains a switching power supply, synchronized with the main oscillator to minimize noise.
Input to the card is 25 - 28V DC.
PROGRAM DISTRIBUTION CARD
It interfaces the intercom system to an external program source and allows the subscribers to
activate and connect program- (music) and alarm channels.
Implementing this feature to the system will reduce the total number of subscribers by 8 per stage.
SUBSCRIBER CARD
It terminates the lines for 8 subscribers, and is the interface card between the stations and the central unit.
The card splits up the audio/signaling information to/from the subscribers. All subscriber cards are identical.
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