6-3
6.2.4
BILATERAL AUDIO CIRCUITRY
The receiver audio path in the Front Panel/Controller Assembly is from the bilateral,
balanced SEABUSS audio terminals (P1, Pins 6 and 7), through the balanced to
unbalanced audio line receiver (U10A), the squelch gate (Q6), the volume control
(R2) and the audio power amplifier (U14) to the loudspeaker. The squelch limiter
(U9A and U9B) connects to the audio upstream of the squelch gate. The hard
limited output of the limiter is connected to the input of the controller CPU, U1.
The transmitter audio path is from the microphone to the microphone mute
transistor (Q5) and from there on to the microphone amplifier/SEABUSS driver
consisting of U10C and U10D. SEABUSS audio level is nominally 2.0 volts peak-
to-peak (0dBm).
6.2.5
SEABUSS DATA CIRCUITRY
The serial data stream which links the controller(s) and the transceiver connects to
the controller(s) at P1, Pins 4 and 5. The data transducer is a bidirectional data
transceiver (U6) which uses a bi-phase data format similar to RS485. On each end
of the data path, the data transceivers are connected to the system CPU boards
through the Sout and Sin pins on the data transceiver. Communications between the
controller(s) and the SEA 245 Mainboard Assembly are bidirectional and fully
interactive. This means that when the SEA 2450 Remote Controller is used, the
status of the SEA 245 is reflected at both operating stations. Controller-SEA 245
data is sent in packets and is error checked. Collision protection is provided for all
data sources. Baud rate is 9600 bps. For further data on the format of the
SEABUSS command structure used in the SEA 245, contact SEA, INC. at 7030
220th St. S.W., Mountlake Terrace, WA, 98043. Or call (425) 771-2182.
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