A Clear-Com SB-704 Four-Channel Switchboard Main Station in very good condition. This unit is fully functional. This unit's rack has been decommissioned and it is no longer needed. Here is some information from the manufacturer.

Description

The SB-704 is a 2RU four-channel switchboard main station with programmable front

panel buttons, individual channel short-circuit protection, individual channel volume control, a

switchboard matrix, and a regulated fail-safe power supply. The SB-704 supports up to 55

beltpacks or 10 speaker stations, or 12 headset stations. The 10 x 4 assignment switching

matrix allows up to 10 different groups of stations to be assigned to any one of the four channels.

Audio Sources and Monitoring

The SB-704 accepts five separate program audio sources: four line-level balances inputs and

one assignable line-level input. The assignable program input accepts a balanced signal and is

designed for monitoring external audio. The four balanced program inputs can be used to create

individual program feeds on the intercom channels. The SB-704 can monitor intercom activity

on one or all four channels with individual volume level controls. Monitoring intercom activity is

possible through a headset.

Talk Selection

The SB-704 has mic pre-amps with limiters and speech-shaping circuits. An individual electronic

momentary/latching Talk button is available for each channel. Illuminated dual-action Talk buttons

light an LED dimly when latched: blue-color while in standby, amber-color when latched. The

latching feature can be disabled. The channels can be accessed separately or simultaneously

without tying them together. A selector switch toggles between the headset or microphone. The

Talk buttons can also be controlled with a footswitch.

Announce Output

For paging, the SB-704 provides a balanced, line-level output signal to a ¼-inch TRS connector

on the rear panel. The front panel Announce button activates the output and the Announce relay.

The relay circuit, on a separate ¼-inch TRS connector, is typically used to mute monitors.

Call Signaling

The SB-704 has individual Call buttons with visual call signaling for each channel on the partyline.

The visual signal will flash brightly and will emit an audible signal if the remote station operator

holds the Call button for more than 2 seconds. The call signaling feature can be programmed to the Talk buttons.