IC1: 450KHz to 950KHz		DL01 (Digital local oscillator 1?)
				Mixed to produce 4.450MHz to 4.950MHz

IC2: 1.625MHz			LO3 (Local oscillator 3)
				Chopped to produce 8.375Mhz

IC3: 1.17MHz			MCAR generation (SSB, FSCK) (feeds IC2)
				Chopped to produce 8.83MHz

				CW STON (CW mode)

				FM subtone (FM mode)

IC4: 455KHz			CAR generation (AM mode?)

				FSK modulation in FSK mode


IC1 MDEN ground
IC2 MDEN +5V
IC3 MDEN controlled by RTK signal (RTTY keyer input)
IC4 MDEN controlled by RTK signal (RTTY keyer input)

IC1 SPSL +5V
IC2 SPSL controlled by TOC on PLL unit (Sub-tone control)
IC3 SPSL +5V
IC4 SPSL +5V

MDEN - SPSL

MDEN 0 + SPSL X == no phase offset (X == don't care)
MDEN 1 + SPSL 1 == serial phase offset
MDEN 1 + SPSL 0 == direct phase offset

IC1: no phase ever
IC2: either serial or parallel phase
IC3: either serial or no phase
IC4: either serial or no phase