Kenwood TM-2550A Service Manual

Also see for TM-2530A: Instruction manual Instruction manual Instruction manual Instruction manual Instruction manual

TM-2550A/E,2530A10CIRCUIT DESECRIPTIONDTMF circuit (K,M Type)TheDTMF(DualToneMultipleFrequency)signalisgene-ratedbyIC4:LR4087ontheCONTROLunit.Powerforthetonegeneratorisobtainedfromthe8T(8voltsontransmit)line.DuringreceivetheICisgroundedpreventingunwantedtonegeneration.Duringtransmitthenon-exclusiveportR9OisalogicHigh,causingpull-up resistorsP10thruP13toopenallowingtheDTMFsignals tobegeneratedbypressingoneofthekey-boardkeys.During automatic transmission of telehphone number infor-mation port R90 is a logic Low, connecting pull-up resistorsP10 thru P13. P10 thru P13 apply a logic High, and P70thru P73 a logic low, so that the desired DTMF signals aregenerated. While the DTMF signal is being generated IC4(CONTROL unit) mutes the normal transmitted audio._—_ —_ —_ . — a eei 5V - IC4 : LR408710 oscaor | MES MEOUT “IN z |ak 42 ar: os O13 yy 3 -_-— |—f 84 EH _*ie Rt OSC OUT 04 4S 4S fs | O14 43 16 |oe eee eee kt R2 TOOUTE> TT | | |7 |s |9 [Lo j O15 yo care L Jmmm rm 1 R3 C3 |Sy ty oy Us j IN 4 L2M 9 rs rs ; OG ,, car |mM —_t}So oy co Ce R4 Ct |. |\t ||K,MTYPE ONLY |‘ | oYP10 P11 P12 P13. R73 R72 R71 R70(K1) (K2) (K3) (K4) (KB) (K7) (K6) (KS)Yv vKEY SCAN KEY RETURN R30Fig. 12 DTMF circuitR1 R2 R3 R4 VE ove141312) 1 — — — — © - ——7ANA Vt MUTE| mM KB>—] 50 OUT—— Why| $—w- || [yggare var ve || SIGN D/A |ROW WAVE b+ TERCOUNTER Jw— COUNTER CONVER TONEOUTCOLUMN SIGN D/A VeCOUNTER ja—@ COUNTER | CONVERTER |KEYBOARD __f VKB || Locic Le yvxs V+ XMTR| : swAAO 48) SINGLE TONEWw ~ INHIBITWye VV —3445 HO — eo ——— ——— — — IJci c2 C3 C4Fig.13 LR4087 Block diagram (Control unit 1C4) K, M type only