diff --git a/bmspy/jbd_ups.py b/bmspy/jbd_bms.py
similarity index 95%
rename from bmspy/jbd_ups.py
rename to bmspy/jbd_bms.py
index 51c9f68..003e8a8 100644
--- a/bmspy/jbd_ups.py
+++ b/bmspy/jbd_bms.py
@@ -6,14 +6,15 @@ import atexit
 import serial
 import serial.rs485
 import time
+from collections.abc import Iterator
 from dataclasses import dataclass, fields as dataclass_fields
 
 from bmspy.utilities import debugger
-from bmspy.classes import BMSScalarField, BMSMultiField, BMSInfoField
+from bmspy.classes import BMSScalarField, BMSMultiField, BMSInfoField, BMSField, UPS
 
 
 @dataclass
-class JBDUPS:
+class JBDBMS(UPS):
     bms_voltage_total_volts: BMSScalarField | None = None
     bms_current_amps: BMSScalarField | None = None
     bms_capacity_remaining_ah: BMSScalarField | None = None
@@ -42,7 +43,7 @@ class JBDUPS:
     bms_temperature_celcius: BMSMultiField | None = None
     bms_voltage_cells_volts: BMSMultiField | None = None
 
-    def items(self):
+    def items(self) -> Iterator[tuple[str, BMSField]]:
         """Yield (name, field) for all non-None BMS field attributes."""
         for f in dataclass_fields(self):
             v = getattr(self, f.name)
@@ -50,7 +51,7 @@ class JBDUPS:
                 yield f.name, v
 
 
-def serial_cleanup(ser, debug=0):
+def serial_cleanup(ser: serial.Serial, debug: int = 0) -> None:
     if debug > 2:
         debugger("serial: cleaning up...")
     if ser.is_open:
@@ -59,7 +60,7 @@ def serial_cleanup(ser, debug=0):
         ser.close()
 
 
-def initialise_serial(device, debug=0):
+def initialise_serial(device: str, debug: int = 0) -> serial.Serial:
     ser = serial.Serial(device, baudrate=9600)
     ser.parity = serial.PARITY_NONE
     ser.bytesize = serial.EIGHTBITS
@@ -72,12 +73,12 @@ def initialise_serial(device, debug=0):
     return ser
 
 
-def calculate_checksum(msg):
+def calculate_checksum(msg: bytes | bytearray) -> str:
     checksum = ""
     return checksum
 
 
-def verify_checksum(data, checksum):
+def verify_checksum(data: bytes | bytearray, checksum: bytes) -> bool:
     # (data + length + command code) checksum, then complement, then add 1, high bit first, low bit last
     # data should have start/rw stripped
     s = 0
@@ -88,7 +89,7 @@ def verify_checksum(data, checksum):
     return s == chk
 
 
-def convert_to_signed(x):
+def convert_to_signed(x: int) -> int:
     # For values below 1024, these seem to be actual results
     # For values above 1024, these seem to be encoded to account for high and negative floats
     max_uint = 1024
@@ -98,14 +99,14 @@ def convert_to_signed(x):
         return x
 
 
-def bytes_to_digits(high, low):
+def bytes_to_digits(high: int, low: int) -> int:
     result = high
     result <<= 8
     result = result | low
     return result
 
 
-def bytes_to_date(high, low):
+def bytes_to_date(high: int, low: int) -> str:
     result = bytes_to_digits(high, low)
     day = result & 0x1F
     mon = (result >> 5) & 0x0F
@@ -113,7 +114,7 @@ def bytes_to_date(high, low):
     return "{:04d}-{:02d}-{:02d}".format(year, mon, day)
 
 
-def requestMessage(ser, reqmsg, debug=0):
+def requestMessage(ser: serial.Serial, reqmsg: bytearray, debug: int = 0) -> bytes | str | bool:
     if debug > 2:
         debugger("serial: starting up monitor")
     if ser.is_open:
@@ -172,7 +173,7 @@ def requestMessage(ser, reqmsg, debug=0):
         debugger("serial: cannot open port")
 
 
-def parse_03_response(response, debug=0):
+def parse_03_response(response: bytearray, debug: int = 0) -> JBDBMS | bool:
     # Response is 34 bytes:
     # 00        begin:  \xDD
     # 01        r/w:    \xA5
@@ -219,7 +220,7 @@ def parse_03_response(response, debug=0):
     if data_len == 0:
         return False
 
-    result = JBDUPS()
+    result = JBDBMS()
 
     vtot = bytes_to_digits(response[4], response[5]) * 0.01
     result.bms_voltage_total_volts = BMSScalarField(
@@ -431,7 +432,7 @@ def parse_03_response(response, debug=0):
     return result
 
 
-def parse_04_response(response, debug=0):
+def parse_04_response(response: bytearray, debug: int = 0) -> BMSMultiField | bool:
     # Response is 7 + cells * 2 bytes:
     # 00        begin:  \xDD
     # 01        r/w:    \xA5
@@ -496,7 +497,7 @@ def parse_04_response(response, debug=0):
     )
 
 
-def collect_data(ser, debug=0):
+def collect_data(ser: serial.Serial, debug: int = 0) -> JBDBMS | bool:
     # Request is 7 bytes:
     # \xDD for start
     # \xA5 for read, \x5A for write
diff --git a/bmspy/server.py b/bmspy/server.py
index 7c0b9f0..ca6acb1 100755
--- a/bmspy/server.py
+++ b/bmspy/server.py
@@ -15,7 +15,7 @@ from dataclasses import asdict as dataclass_asdict
 from typing import Any, NoReturn
 
 from bmspy.utilities import debugger
-from bmspy.jbd_ups import collect_data, initialise_serial
+from bmspy.jbd_bms import collect_data, initialise_serial
 
 # Expected kernel log output when the USB-serial adapter is plugged in:
 # usb 1-1.4: new full-speed USB device number 4 using xhci_hcd