## Signal Boxes by Ploy

### Puzzle explanation

The puzzle’s theme was the LOGIC of George BOOLE, the English mathematician and philosopher, as realised in CIRCUIT form by Claude SHANNON, the American engineer and information theorist. Together, their work underpins much of today’s digital electronics. Six columns of the grid contained ten clashes between O and I, to be interpreted as signals 0 and 1. The intervening columns contained five logic circuit elements (OR, NOT, AND, NAND — not AND, since all were to be different — and NOR), giving a circuit with five inputs and one output. The four theme words resolved some of the clashes, the remainder being resolved using the logic circuit definitions in Chambers Dictionary. Modified words, Across: 17 viol 20 siri 21 oaty 28 ciao 34 lignin 37 noon; Down: 6 Capitol 30 non-iron 36 ocrea.

### Clue explanations

Conventions: * = anagram, < = reversal

Across
1 STEP-UP First letters
7 EPACT EP + ACT
12 HAPU (U + PAH) <
13 DE LA MARE DELAWARE, M in place of W
15 TERAPH TELEGRAPH – (L + EG)
16 SCRY SCREWY – (E + W); Bridge partners
17 VIOL First letters & lit
18 NEBISH NESH about (B + I)
20 SIRI INDIRA’S * – AND *
21 OATY O + AT + Y
23 ULE (m)ULE(s)
25 TAN Alternate letters of TRAIN; answer is a colour
26 INNERS WINNERS – W
28 CIAO Alternate letters
30 NICE NI(e)CE
33 WAAC WC (can) about (A + A)
34 LIGNIN (a)LIGNIN(g)
35 BLINI BLING, I for G
37 NOON N + (bistr)O + ON
38 OFT First letters
40 RORTY R in middle of TORY *
41 FALAJ F + A + JAL <
42 EYRIR ER about (YR + I)
43 ELEGANCE EL + (CE after (E + GAN(try))
44 ALP Hidden reversed & lit
45 ÂME DAMNÉE (E’EN + MADE + MA) <
Down
1 SHIV SHIVA (Siva) – A
2 TABOO O in BOAT *
3 PUTLOG TUP < + LOG
4 PEREIA (r)EPAIRE(d) *
5 ALABANDINE (À L’ABANDON, I for O) + E
6 CAPITOL POLITICA(l) * – I & lit
8 PASHA PASH + A
9 ARCADE (C + A + ’D) in ARE
10 CERCI Homophone (Circe)
11 TRYST TRY + ST; reference Beano comic
13 DENOTABLE ((nati)ONAL + DEBT) * + E
14 FORECASTLES SOFT CEREALS *
19 SYNANDRIUM DANNY * in MUIRS <
20 SUBWOOFER USE OF BOW * + (sita)R
24 LEAF-FALL LE + ALFALF(a) *
27 SEA NYMPH HE-MAN SPY *
29 ILIA I + AIL <
30 NON-IRON NORIMON <, N for M
31 INORB B after (IN + OR)
32 CUITTLE (IT + T) in CLUE *
36 OCREA (CORE, O to top) + A
39 GAGA GAG + A
42 ENE Hidden