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2.5 Do any CED players have a serial port to control the player withan external computer?




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This article is from the RCA SelectaVision VideoDisc FAQ, by tom@cedmagic.com (Tom Howe) with numerous contributions by others.

2.5 Do any CED players have a serial port to control the player withan external computer?

RCA made four models controllable with an external computer- the SKT265,
SJT400, SJT400X, and SKT400. The SKT265 was intended only for
institutional use, as the additional circuitry was mounted on an
external circuit board wired to the unit with a ribbon cable. On the
back of the SKT265 was a 15 pin serial port similar to those used on
computer-controllable LaserDisc players. The SJT400 and SKT400 players
had an RCA-style jack in the back simply labeled "Control" that could be
used with an external computer. RCA was deliberately vague on the
purpose of this jack, stating in the owner's manual that the jack was
for "connection with accessory equipment that may become available in
the future," and making no definition of it at all in the technical and
service manuals. By disassembling the player, and tracing the control
jack's lead to J6107 on the FEATURES/RKM/CAV board, the circuitry
associated with the control jack can be assessed from the player's
schematic. The control jack lead connects to the remote keyboard
microcomputer through a receiver/driver transistor network, meaning the
jack can both transmit and receive data over a single piece of wire. The
external computer has to transmit its data in a handshaking protocol the
remote keyboard microcomputer can understand. The control jack was used
in the short-lived Bally NFL Football arcade game to display live action
from a VideoDisc. And in addition, an interface to attach the 400 series
player to the ColecoVision video game system and ADAM home computer was
planned, but RCA's abandonment of the CED system halted this project in
the prototype stage.

The control jack reappeared in RCA's Dimensia system in late 1984 as the
common method for all the individual audio/video components to communicate
with one another. RCA's prototype SKT425 player was going to be an
integral part of Dimensia, but since this was after the cancellation of
CED, RCA made no mention of this in any of the Dimensia announcements or
literature. But the control circuitry is still fully compatible, so any
400 series player can be added to the Dimensia control bus.


 

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previous page: 2.4 The RCA K series players appear externally identical to their Jseries counterparts. What changes were made in the K series?
  
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next page: 2.6 Is it true that new stylus cartridges for CED players have beenunavailable for a long time?