TK-521020TERMINAL FUNCTIONPin Name I/O FunctionNo.Pin Name I/O FunctionNo.Control unit (X57-6820-XX B/5)Pin Name I/O FunctionNo.35 CH_A O Rotary switch output 136 33A - 3.3V37 CH_B O Rotary switch output 238 25D - 2.5V39 CH_C O Rotary switch output 340 15D - 1.5V41 CH_D O Rotary switch output 442 15D - 1.5V43 PTT O PTT output44 5M - 5V45 NC - No connection46 5M - 5V47 oE I Shift register OE48 LCDV - LCD contrast control voltage49 DGND - GND50 DGND - GNDCN6031 INT SP- O BTL output - for internal speaker2 INT SP- O BTL output - for internal speaker3 INT SP+ O BTL output + for internal speaker4 INT SP+ O BTL output + for internal speaker5 INT MIC+ I Internal MIC input6 INT MIC- - Internal MIC GNDCN604 (K2 and K3 models only)1 A0 I Adrress bus 02 GND - GND3 WR I WR bus4 RD - No connection5 D7 I/O Data bus 76 D6 I/O Data bus 67 D5 I/O Data bus 58 D4 I/O Data bus 49 D3 I/O Data bus 310 D2 I/O Data bus 211 D1 I/O Data bus 112 D0 I/O Data bus 013 GND - GND14 LCS I LCD chip selectCN751 (K2 and K3 models only)1 V4 - LCD drive power supply2 V3 - LCD drive power supply3 V2 - LCD drive power supply4 V1 - LCD drive power supply5 V0 - LCD drive power supply6 VR - V0 voltage adjustment terminal7 NC - No connection8 NC - No connection9 NC - No connection10 NC - No connection11 NC - No connection12 NC - No connection13 Vout - Raising voltage output14 VDD - 3.3V37 CH_B I Rotary switch input 238 25D - 2.5V39 CH_C I Rotary switch input 340 15D - 1.5V41 CH_D I Rotary switch input 442 15D - 1.5V43 PTT I PTT input44 5M - 5V45 NC - No connection46 5M - 5V47 oE O Shift register OE48 LCDV - LCD contrast control voltage49 DGND - GND50 DGND - GNDCN6011 GND - GND2 GND - GND3 MIC O External MIC output4 MICE - External MIC GND5 SP+ O BTL output + for external speaker6 PWR I Power control input7 SP+ O BTL output + for external speaker8 15V - 15V9 SP- O BTL output - for external speaker10 SB1 O Battery Level output11 SP- O BTL output - for external speaker12 +B - Power input after passing through the fuse13 AF I Audio input14 +B - Power input after passing through the fuse15 VOL O Volume level output16 +B - Power input after passing through the fuse17 CLK I Clock data input18 +B - Power input after passing through the fuse19 GND - GND20 LRST I LCD reset input21 KIN O Key output22 28M - 2.8V23 EXAFC I External AF input24 PSW O Power output after power switch25 KES I Key counter clear to send26 INAFC I Internal AF input27 DAT I Data input28 ECSW I Echo cancel MIC switch29 TGL0 O Lever switch output 030 33M - 3.3V31 TGL2 O Concentric switch output 232 33M - 3.3V33 TGL1 O Concentric switch output 134 33A - 3.3V