Specifications

converter providing a balanced left and right output. The unit features a front panel headphone output and

volume control for easy confidence monitoring. The AES-302 can be used as a totally automatic switcher

sensing loss of clock or any error displayed on the front panel to command the switcher to select the

alternate feed. In addition to digital error switching, the unit features a silence sense circuit for switching

upon audio failure conditions. All automatic switching functions are user defined and can be initialized

with a simple DIP switch setting upon installation of the unit. Command of the switcher can also be

performed manually at the front panel or remotely.

Remote control of the unit is accessed through the rear panel 9 pin D connector. Simple momentary ground

closure to the appropriate pin selects channels and error reset. Status of channel selected and error flag is

also available at this connector. Refer to the pin out table 3 on page 6 for connection information. The

interface is compatible with open collector command. The AES-302 supplies +15 V.D.C. for powering

open collector actuators.

Two additional features that have been added to later production AES-302 units includes power fail feed

through of the selected input to AES output #1 and a delay circuit has been added to the automatic

switching function. With no power connected to the unit, the AES-302 will pass the last selected input

signal to the #1 AES output through K3 NC contacts. Upon power application K3 energizes and AES #1

output receives its signal from U2 RS-485 driver. The additional delay was added to prevent the unit from

switching on momentary glitches that can occur in STL equipment. An added 3 seconds to the switching

time prevents the unit from switching under transient conditions.

V. Initial Operating Set up

Attach input and output connections to the unit using the appropriate connector. The unit can be supplied

with XLR, S.P.D.I.F., or optical connectors at any of the inputs or outputs. If the connector scheme

supplied is not the one desired, consult the factory for a field or factory connector modification.

Plug the remote control plug in and tighten the connector screws in place.

You may select any or all of the error flag and/or silence sense switching, which will command the

switcher to switch to the alternate path. The “no lock” position S6-2 is always selected for automatic

operation. Other error flags and the silence sense error are selected by placing the designated DIP switches

to the on position. Refer to the theory of operation section table 1 on page 5 for possible settings. Once

this is done, the unit is ready to be powered up for operation. The default setting is to command the

switcher upon loss of clock. When the silence sense error is selected for switching, there are several

configurations possible. It is possible to monitor both left and right channels and switch upon complete

audio loss or to have the silence sensor switch upon loss of left or right channel individually. This feature

was added so that non correlated audio feeds can cause the silence sensor to switch where one feed may

take precedence over another. Selection of L+R, Left, or Right only audio is done by placing the proper

jumpers on the motherboard. Refer to the theory of operation section table 2 on page 5 for the various

settings.

Once power is applied and a valid AES bit stream is applied to the selected input, the unit will default to

“Manual” mode of operation. The LED indicator over the “Manual” button should be illuminated. In

addition, the channel selected LED indicator will be lit. There should also be an indication of sample

frequency. Press the error-reset button to clear any errors that might be indicated. If the digital audio stream

feeding the active channel of the unit is valid and no errors occur the unit is ready for to be placed in the

automatic mode if desired. If any of these errors occur after depressing the error-reset button, then the feed

to the unit is defective and should be investigated. If all is in order, the unit is now ready for operation. All

that is left to do is to select the desired feed and then if desired, place the unit in automatic switch mode by

depressing the “Auto” button. The LED indicator will light indicating automatic control of the switcher.

The unit will remain in this mode until an error is detected, loss of lock occurs, silence is detected or the

alternate feed is manually selected. If any of these events occur, the unit will switch to the alternate path