TELEBYTE TECHNOLOGY, INC.
MODEL 420
| 
 Modem Type  | 
 Data (synchronous)  | 
| 
 Maximum Data Rate  | 
 128Kbps  | 
| 
 Data Bus  | 
 External  | 
| 
 Data Modulation Protocol  | 
 Proprietary  | 

| 
 CONNECTIONS  | |||
| 
 Purpose  | 
 Location  | 
 Purpose  | 
 Location  | 
| 
 DC power  | 
 CN1  | 
 Receive  | 
 CN4  | 
| 
 RS-232/422  | 
 CN2  | 
 Transmit  | 
 CN5  | 
| 
 Ground  | 
 CN3  | ||
| 
 CARRIER ON  | |
| Setting | 
 SW2/C  | 
| » Always on | 
 On  | 
| RTS high | 
 Off  | 
| 
 GROUND  | |
| Setting | 
 JP1  | 
| » Frame and signal ground connected | 
 Pins 1 & 2 closed  | 
| Frame and signal ground separate | 
 Pins 3 & 4 closed  | 
| 
 IMPEDANCE  | |
| Setting | 
 JP2  | 
| » 135 Ohms(low) | 
 Pins 1 & 4 closed  | 
| High | 
 Pins 3 & 4 closed  | 
| 
 LINE SPEED  | ||||||
| Speed | 
 SW1/A  | 
 SW1/B  | 
 SW1/C  | 
 SW1/D  | 
 SW1/E  | 
 SW1/F  | 
| 32Kbps | 
 Up  | 
 Down  | 
 Down  | 
 Down  | 
 Down  | 
 Down  | 
| 48Kbps | 
 Down  | 
 Up  | 
 Down  | 
 Down  | 
 Down  | 
 Down  | 
| 56Kbps | 
 Down  | 
 Down  | 
 Up  | 
 Down  | 
 Down  | 
 Down  | 
| » 64Kbps | 
 Down  | 
 Down  | 
 Down  | 
 Up  | 
 Down  | 
 Down  | 
| 72Kbps | 
 Down  | 
 Down  | 
 Down  | 
 Down  | 
 Up  | 
 Down  | 
| 128Kbps | 
 Down  | 
 Down  | 
 Down  | 
 Down  | 
 Down  | 
 Up  | 
| 
 RECEIVE CLOCK  | |
| Setting | 
 SW/H  | 
| » Disabled | 
 Down  | 
| Enabled | 
 Up  | 
| 
 RTS/CTS DELAY  | ||
| Setting | 
 SW2/A  | 
 SW2/B  | 
| » Disabled | 
 Off  | 
 Off  | 
| 7ms | 
 On  | 
 Off  | 
| 60ms | 
 Off  | 
 On  | 
| 
 TRANSMIT CLOCK SOURCE  | |
| Setting | 
 SW1/G  | 
| » Internal | 
 Down  | 
| External | 
 Up  | 
| 
 FACTORY CONFIGURED SETTINGS  | |
| 
 Jumper  | 
 Setting  | 
| 
 SW2/D  | 
 Not used  | 
| 
 DIAGNOSTIC LED(S)  | |||
| 
 LED  | 
 Color  | 
 Status  | 
 Condition  | 
| 
 PWR  | 
 Red  | 
 On  | 
 Power is on  | 
| 
 PWR  | 
 Red  | 
 Off  | 
 Power is off  | 
| 
 TD  | 
 Red  | 
 On  | 
 Modem is transmitting data  | 
| 
 TD  | 
 Red  | 
 Off  | 
 Modem is not transmitting data  | 
| 
 RD  | 
 Red  | 
 On  | 
 Modem is receiving data  | 
| 
 RD  | 
 Red  | 
 Off  | 
 Modem is not receiving data  | 
| 
 RTS  | 
 Red  | 
 On  | 
 RTS signal is high  | 
| 
 RTS  | 
 Red  | 
 Off  | 
 RTS signal is low  | 
| 
 DCD  | 
 Red  | 
 On  | 
 Carrier signal detected  | 
| 
 DCD  | 
 Red  | 
 Off  | 
 Carrier signal not detected  | 
| 
 TM  | 
 Red  | 
 On  | 
 Modem is in test mode  | 
| 
 TM  | 
 Red  | 
 Off  | 
 Modem is in test mode  |