rs-uv3a/src/content/docs/reference/commands/system.md

---
title: System Commands
description: Power, status, and configuration commands for the RS-UV3A
---

## TX – Transmit

Controls the transmitter.

### Syntax

```
TXn
```

### Parameters

| Value | Description |
|-------|-------------|
| 0 | Stop transmitting (return to RX) |
| 1–5 | Transmit with n-minute timeout |

### Examples

```
TX1             # Transmit, 1 minute max
TX3             # Transmit, 3 minute max
TX0             # Stop transmitting
```

### Notes

- `TX0` stops TX even if hardware PTT is held
- Timeout overrides `TO` setting for this transmission only
- If TX is off, radio is in RX mode

---

## PW – TX Power

Sets the transmit power level.

### Syntax

```
PWn
PW?
```

### Parameters

| Value | Power Level |
|-------|-------------|
| 0 | Low (~10 mW, 10 dBm) |
| 1 | High (~200 mW, 23 dBm) |

### Default

1 (High)

### Examples

```
PW1             # High power
PW0             # Low power
PW?             # Query current setting
```

---

## TO – Timeout

Sets the transmit timeout timer.

### Syntax

```
TOnnn
TO?
```

### Parameters

| Parameter | Range | Description |
|-----------|-------|-------------|
| `nnn` | 000–600 | Timeout in seconds |
| | 000 | Disable timeout |

### Default

000 (disabled)

### Examples

```
TO180           # 3 minute timeout
TO300           # 5 minute timeout
TO000           # No timeout
TO?             # Query current setting
```

### Notes

- All 3 digits required
- When timeout occurs, sends TG message and unkeys
- Protects against stuck PTT

---

## TG – Timeout Message

Sets the CW message sent when TX times out.

### Syntax

```
TG<text>
TG?
```

### Parameters

| Parameter | Description |
|-----------|-------------|
| `<text>` | Message up to 7 characters |

### Default

'TO'

### Examples

```
TGTIME          # Send "TIME" on timeout
TGTO            # Send "TO" (default)
TG?             # Query current message
```

---

## HT – Hang Time

Sets TX hang time for repeater applications.

### Syntax

```
HTnnnn
HT?
```

### Parameters

| Parameter | Range | Description |
|-----------|-------|-------------|
| `nnnn` | 0000–5000 | Hang time in milliseconds |

### Default

0000 (no hang time)

### Examples

```
HT1500          # 1.5 second hang time
HT2000          # 2 second hang time
HT0000          # No hang time
HT?             # Query current setting
```

### Notes

- All 4 digits required
- TX stays keyed for specified time after PTT release
- Used with courtesy beep in repeater applications

---

## CO – COR Inhibit

Sets the COR (Carrier Operated Relay) inhibit time.

### Syntax

```
COnnnn
CO?
```

### Parameters

| Parameter | Range | Description |
|-----------|-------|-------------|
| `nnnn` | 0000–9999 | Inhibit time in milliseconds |

### Default

0000

### Examples

```
CO0150          # 150 ms inhibit
CO0200          # 200 ms inhibit
CO?             # Query current setting
```

### Notes

- Prevents COR from going active briefly after TX ends
- Avoids squelch noise triggering COR
- Useful for packet and repeater applications

---

## CB – Courtesy Beep

Sets the courtesy beep for repeater applications.

### Syntax

```
CBn
CB?
```

### Parameters

| Value | Beep |
|-------|------|
| 0 | None |
| 1 | Low tone |
| 2 | High tone |
| 3 | High/low |
| 4 | Two tones |

### Default

0 (none)

### Examples

```
CB0             # No beep
CB2             # High tone beep
CB?             # Query current setting
```

### Notes

- Sounds after hang time expires
- Signals repeater is ready for next transmission

---

## VX – VOX

Enables or disables voice-operated transmit.

### Syntax

```
VXn
VX?
```

### Parameters

| Value | Description |
|-------|-------------|
| 0 | VOX off |
| 1 | VOX on |

### Default

0 (off)

### Examples

```
VX1             # Enable VOX
VX0             # Disable VOX
VX?             # Query current setting
```

### Notes

- Pressing PTT disables VOX
- Do not use with speaker-mic (RX audio will trigger TX)
- Sensitivity set by `VL` command

---

## VL – VOX Level

Sets VOX sensitivity.

### Syntax

```
VLn
VL?
```

### Parameters

| Value | Sensitivity |
|-------|-------------|
| 0 | High (most sensitive) |
| 1 | Medium |
| 2 | Low (least sensitive) |

### Default

1 (Medium)

### Examples

```
VL0             # High sensitivity
VL2             # Low sensitivity
VL?             # Query current setting
```

---

## BW – Bandwidth

Sets the channel bandwidth.

### Syntax

```
BWn
BW?
```

### Parameters

| Value | Bandwidth |
|-------|-----------|
| 0 | 12.5 kHz (narrow) |
| 1 | 25 kHz (wide) |

### Default

1 (25 kHz)

### Examples

```
BW1             # 25 kHz (standard)
BW0             # 12.5 kHz (narrow)
BW?             # Query current setting
```

### Notes

- **Requires power cycle to take effect**
- Use narrow for crowded bands
- Some repeaters require narrow bandwidth

---

## PD – Power Down

Controls the transceiver chip power.

### Syntax

```
PDn
PD?
```

### Parameters

| Value | Description |
|-------|-------------|
| 0 | Chip powered down |
| 1 | Chip powered on |

### Default

1 (on)

### Examples

```
PD0             # Power down (saves ~70 mA)
PD1             # Power up
PD?             # Query state
```

### Notes

- Reduces current by approximately 70 mA
- Radio cannot TX/RX when powered down
- Serial commands still work

---

## B1 – Baud Rate 1

Sets the baud rate for serial port 1 (USB/JP1/JP2).

### Syntax

```
B1n
B1?
```

### Parameters

| Value | Baud Rate |
|-------|-----------|
| 0 | 1200 |
| 1 | 4800 |
| 2 | 9600 |
| 3 | 19200 |
| 4 | 38400 |
| 5 | 57600 |

### Default

3 (19200)

### Examples

```
B13             # Set to 19200
B15             # Set to 57600
B1?             # Query current setting
```

### Notes

- **Requires power cycle to take effect**
- Reconnect terminal at new baud rate after power cycle

---

## B2 – Baud Rate 2

Sets the baud rate for serial port 2 (DB-9 I/O connector).

### Syntax

```
B2n
B2?
```

### Parameters

Same as B1.

### Default

3 (19200)

### Notes

- Only applies when `EX1` (serial mode)
- **Requires power cycle to take effect**

---

## FW – Firmware Version

Reports the current firmware version.

### Syntax

```
FW
```

### Response

```
FW: 2.4A
```

### Notes

- Query only, no parameters

---

## BL – Bootloader

Enters bootloader mode for firmware updates.

### Syntax

```
BL
```

### Notes

- RS-UV3A waits indefinitely for bootloader connection
- Power cycle required to exit without updating
- See [Firmware Upgrade](/guides/firmware-upgrade/) guide

---

## SS – Signal Strength

Reads the current receiver signal strength.

### Syntax

```
SS
```

### Response

```
SS: -85
```

Value is in dBm.

---

## SN – Noise Level

Reads the current receiver noise level.

### Syntax

```
SN
```

### Response

```
SN: 1234
```

### Notes

- Lower values indicate cleaner signal
- Raw value, not calibrated

---

## VT – Voltage

Reads the operating voltage.

### Syntax

```
VT
```

### Response

```
VT: 8.5V
```

### Notes

- Reads the 8.5V internal rail
- Useful for monitoring power status

---

## TP – Temperature

Reads the PCB temperature.

### Syntax

```
TP
```

### Response

```
TP: 42
```

Temperature in °C.

### Notes

- PCB temperature, not ambient
- Will be warmer during TX

---

## BS – Battery Status

Legacy command for battery charger status.

### Syntax

```
BS
```

### Response

```
BS: 0
```

or

```
BS: 1
```

### Notes

- RS-UV3A Rev A does not have battery charging
- Included for compatibility with older RS-UV3 versions

---

## RR – Register Read

Reads an RDA1846S transceiver chip register. **Advanced use.**

### Syntax

```
RRxx
```

### Parameters

| Parameter | Description |
|-----------|-------------|
| `xx` | Register address in hex |

### Response

Returns 16-bit hex value.

### Notes

- For advanced debugging only
- Register documentation available online for RDA1846S

---

## RS – Register Set

Sets an RDA1846S transceiver chip register. **Advanced use.**

### Syntax

```
RSxxyyyy
```

### Parameters

| Parameter | Description |
|-----------|-------------|
| `xx` | Register address in hex |
| `yyyy` | 16-bit value in hex |

### Response

```
OK
```

or no response if failed.

### Notes

- Can disrupt radio operation if used incorrectly
- For advanced debugging only
- Settings may not persist through power cycle