IC1	
IC2	SN74LS139 (beebmaster clockbox)
IC3	
IC4	SN74LS30
IC5	SN74LS30
IC6	SN75159
IC7	7805
X1	8MHz crystal
C1	ceramic
C2	ceramic
C3	.22
C4	
C5	
C6	ceramic
C7	elco
C8	
D1	
D2	
D3	
D4	
D5	
D6	
R1	
R2	
RP1	
RP2	
S1	DIL6 switch
S2	DIL6 switch
K1	5-polige DIL socket
K2	5-polige DIL socket

Clock frequency range : 63,5kHz (15,75us) to 4MHz    (250ns)
Clock period range    : 250ns   (4MHz)    to 15,75us (63,5kHz) in 250ns steps
Clock mark range      : 125ns   (8MHz)    to 7,875us (127kHz)  in 125ns steps