The Bogen TBA-15 is a fifteen-watt paging/talkback amplifier approved under Part 68 of FCC rules. The unit permits two-way conversation between a telephone handset, and one or more remote loudspeakers. When used with optional Bogen accessories, paging to zones of loudspeakers is possible. The TBA-15 senses and automatically switches the direction of conversation from telephone to loudspeaker without the use of relays or other moving parts. Control of speech direction is maintained at the telephone handset. Screwdriver-adjustable controls are provided to adjust the switching sensitivity, switching delay (release) time, and loudspeaker and handset volume levels. The TBA-15 talkback frequency response is shaped for maximum intelligibility and background noise rejection. Attack time is less than 5ms. Switchback delay time is adjustable from less than 50ms.to greater than 0.5s to ensure an intelligible flow of conversation. A power on LED and speaker volume control are located on the front panel. A recess in the panel, protected by a removable cover, houses a 600-ohm transformer-coupled telephone line input, 25V/70V constant-voltage outputs, and mute terminals (for unidirectional paging). Controls to adjust sensitivity, switching delay and talkback volume are also located within the panel recess. The amplifier operates from a 120VAC, 60Hz source. A press-to-reset circuit breaker protects the unit from excessive current flow. Safe Operating Area (SOA) and thermal protection safeguard the output device. The unit is finished in black enamel and is easily installed on a wall backboard or in standard 19” equipment racks. Features: --Hands-free reply from loudspeakers --Electronic switching,no relays --25V or 70V balanced line output --Adjustable sensitivity for smooth conversational flow --Safe Operating Area (SOA) and thermal protection for reliability