TM 11-7440-232-12/NAVELEX 0967-LP-275-5010
4-2. SIMPLIFIED PCC BOARD LEVEL CIRCUIT DESCRIPTION
a. Transmit Branch
(1) The primary function of the transmit branch is to convert the serial-by-bit NRZ data at the input to a form
which can be accommodated by the transmission path.
(2) The transmitter clock supplies a 2400 Hz square wave which is derived from the 4.8 MHz RF oscillator.
This output is applied to the encoder, FSK modulator, and the test pattern generator in the transmitter. For high speed
operation, the transmitter clock signal is returned to the clock, amplified, and then supplied to any external equipment
requiring a timing signal. For low speed operation, the encoder portion of the transmitter divides the clock signal by two
and then extends the 1200 Hz signal to the FSK modulator, test pattern generator, and transmitter clock. Operating
speed for the transmitter clock is controlled by the digital receiver clock.
(3) The encoder is used for high speed operation, and is controlled by the clock signal in such a manner that
each data bit is sampled in the middle during the negative transition of the clock signal. This action encodes the original
data to a duobinary form which is then applied to the FSK modulator.