This document shows how to make adapters from DBx connectors to 6-wire 6-position RJ11 (sometimes called RJ12) jacks for various devices. (F) or (M) next to a device name indicates the sex of the connector on the device. The adapter should have the opposite sex.
A diagram showing RJ11 wire numbers is included with each wiring list to reduce errors. RJ11 wire numbers aren't obvious and are typically not printed on the RJ11 jacks. It helps if you always hold an RJ11 jack with the wires up and the leads coming out the back.
For more general information about RJ11 serial communications, return to the RJ11 serial home page.
Devices with DB25 DTE ports include:
RJ11 wire: 1 2 3 & 4 5 6 DB25 wire: HSO 2 7 3 HSI DB25 w/CTS: 4 2 7 3 5 DB25 w/DTR: 20 2 7 3 6
Where HSO/HSI are optional hardware flow control output/input:
Devices with DB25 DCE ports include:
RJ11 wire: 1 2 3 & 4 5 6 DB25 wire: HSO 3 7 2 HSI DB25 w/CTS: 5 3 7 2 4 DB25 w/DTR: 6 3 7 2 20
You have two options: two ports per DB25 connector, neither with hardware flow control, or one port per DB25 connector with hardware flow control. Both options are shown.
Line 1 (no hardware flow control): RJ11 wire: 1 2 3 & 4 5 6 DB25 wire: 3 7 2 Line 2 (no hardware flow control): RJ11 wire: 1 2 3 & 4 5 6 DB25 wire: 6 7 20 One line per DB25 with hardware flow control: RJ11 wire: 1 2 3 & 4 5 6 DB25 w/DTR: 6 3 7 2 20
Use a female DB9 adapter.
RJ11 wire: 1 2 3 & 4 5 6 DB9 wire: 2 7 3
Apparently some wires also need to be jumpered. An old note recommended jumpering 5-6-20 but there is no wire 20.
Use a female DB9 adapter. The hardware flow control lines are necessary for reliable communications because the Galil cannot do XON/XOFF flow control.
RJ11 wire: 1 2 3 & 4 5 6 DB9 wire: 1 2 5 3 4
Use a male DB9 adapter. I suggest disabling flow control because it freezes all process threads; hence the wiring for it is shown in parenthesis.
RJ11 wire: 1 2 3 & 4 5 6 DB9 wire: (4) 3 5 2 (1)
Use a female DB9 adapter. The pinout shown is for RTS/CTS; if you prefer DTR/DSR handshaking then replace DB9 pin 7 with pin 4 and DB9 pin 8 with pin 6
RJ11 wire: 1 2 3 & 4 5 6 DB9 wire: 7 3 5 2 8
Use a male DB9 adapter.
RJ11 wire: 1 2 3 & 4 5 6 DB9 wire: 2 5 3
Use a male DB9 adapter connected to a standard Macintosh DB9 serial port adapter. RS-232 version shown; one may also use RS-422, see Mac serial info elsewhere. Hardware flow control lines are shown in parenthesis; they are optional but recommended for maximum flexibility.
RJ11 wire: 1 2 3 & 4 5 6 DB9 wire: (6) 5 3 & 8 9 (7)
Use a female DB9 adapter. Hardware flow control lines are shown in parenthesis; they are optional but recommended for maximum flexibility. Warning: this jack may not work for all PCs.
RJ11 wire: 1 2 3 & 4 5 6 DB9 wire: (4) 3 5 2 (6,8)
RJ11 wire: 1 2 3 & 4 5 6 DB9 wire: 3 7 2
RJ11 wire: 1 2 3 4 5 6 DB9 wire: 5 2 3
SPC/Voltrex (sold by Newark as SPC) is excellent for DB25 but poor for DB9. The DB25 has a lot of parts and is bulky, but it is solidly built, easy to work with, and the RJ11 doesn't get screwed up by data taps. The DB9 has a lousy RJ11 socket (non-captive wires), and is hard to assemble (cramped space for the wires).
DataComm Warehouse sells a decent model, but the wires are a bit hard to get to because the body doesn't come apart. GC Thorsen (sold by Newark, et. al.) is similar or identical to the DataComm Warehouse model. JAW (dunno the sources) and Data-Spec (sold by Almac) are decent but difficult to take apart.
Avoid the models sold by South Hills Electronics (flimsy), Digi-Key (sticky RJ11 socket and difficult to take apart) and made by AMP (uses non-standard pins! and is badly designed).
