The wiring of a 2-way radio to the DB-9connector on a TW-47 interface can vary depending on the model of the 2-way radio that is going to be interfaced to it. The 2-way radio accessory jack pin out information can be hard to come by, most of the 2-way radio manufacturers don’t post this information on-line, so other methods can be used to determine this information.
Most of the time we recommend to TW-47 users that they purchase a remote PTT MIC speaker unit (Kenwood, Motorola, Yaesu all make various versions of these units) and map the wiring from the MIC / speaker end, then remove the cable with the molded connector(s) from the unit and use it to wire into the DB-9 connector on the TW-47 interface.
The speaker end of the cable assembly should be wired to pins 1 (shield) and 6 (tip) of the DB-9 connector for the TW-47.
The MIC input to TW-47 can be a bit more interesting to wire up, here is where the user has to determine how the PTT on the 2-way radio is activated. Usually it is done in one of three ways:
• Relay Shunting the MIC input (internal jumpers J6 off, J7 off, J8 on for medium MIC gain, MIC input across pin 5 (shield) and 9 (tip) on the DB-9
• Relay in Series with the MIC input (internal jumpers J6 on, J7 off, J8 on for medium MIC gain, MIC input across pin 4 (tip) and 5 (shield) on the DB-9
• Relay across the sleeves of the MIC input (internal jumpers J6 on, J7 off, J8 on for medium MIC gain, MIC input across pin 8 (tip) and 5 (shield) on the DB-9
The J6 jumper provides a DC path for MIC PTT
The J7 and J8 jumpers provide MIC gain levels
J7 and J8 off: +11 to -20 dBu
J8 on: -26 dBu
J7 and J8 on: -30 to -57 dBu
If the user is unsure of the PTT relay mode of operation then try all three wiring modes one at a time until the right mode is determined. Attached below is a detailed document showing the TW-47 DB-9 connector with signal path information and highlighted with each relay mode activation scheme.