This circuit is a two-channel baseband video switcher. Buffer amps Ul/Ql, U4/Q4, and associated components produce a b
uffered 75- video signal, which is routed to switching network K1/K2/K3. Relay K1 selects either of these two video amplifiers and feeds J7. K2 also routes the output of either video amplifier to K3, which passes the selected video channel to J8 or connects J9 to J8. U2 and J3 are audio amplifiers, which drive U7 and J8 (CD4053 analog switches) to route audio from J1 and J2 to either J14/J15, or J10/J11. Also, audio from J12/J13 can be routed to these jacks.