User`s manual

2-19
Cat. No. 510/514 Input/Output Card
The Cat. No. 510 is the input and output part of the CP45. It has two
stereo inputs for optical soundtracks, one mono microphone input, and
six outputs for the front screen speakers. The card is normally fitted
with a Cat. No. 514 optical preamplifier card which converts the solar
cell signals from the projectors into voltages which are handled by the
Cat. No. 510. Gain and equalization for projector slit loss and microphone
gain are set by controls on the card.
The card is normally powered by the bypass transformer if this is
present, otherwise it takes its power from the main power supply
circuitry in the unit. The bypass supply regulator consists of a very
simple zener regulator and ground reference circuit which uses the
minimum of components for very high reliability.
The front screen speaker outputs are switchable to be full-range or four
pole Linkwitz Reilley active crossovers. Each output has a boost circuit
which is designed to compensate for an average perforated screen with
the mouth of the HF horn within one inch of the rear surface. If the unit
is used with speakers which for reasons of space are not mounted
behind the screen or already contain the HF boost, the peaking can be
switched off on each channel individually.
The microphone input has a sensitivity high enough for use with
average low impedance moving coil capsules.
The power amplifier output stages each have a level adjustment to cater
for a very wide range of amplifier sensitivities and the HF outputs can
each be adjusted to cope with the greater efficiency of horn-loaded
loudspeakers.
The potentiometers have transparent cases to make adjusting a
replacement easy.
Cat. No. 511 Main Board
The Cat. No. 511 main board carries all the circuitry for decoding Dolby
A-Type and SR encoded film soundtracks. The unit also carries a wide
range switching power supply which converts a low voltage AC supply
from an external transformer into the various voltages used in the unit.
The board has all the logic switching for the various modes and carries
the electronic volume control circuits for most of the outputs. In use, if
there is any malfunction such as a power rail going out-of-range or a
connection not being properly made, the main board will signal to the
Cat. No. 510 input/output board that there is a fault and will then be
completely removed from the signal path.