diff --git a/escpos/constants.py b/escpos/constants.py
index 67c6e3b..6025ac4 100644
--- a/escpos/constants.py
+++ b/escpos/constants.py
@@ -10,87 +10,127 @@ moved to `capabilities` as in `escpos-php by @mike42 <https://github.com/mike42/
 :license: GNU GPL v3
 """
 
+# Control characters
+# as labelled in http://www.novopos.ch/client/EPSON/TM-T20/TM-T20_eng_qr.pdf
+NUL = '\x00'
+EOT = '\x04'
+ENQ = '\x05'
+DLE = '\x10'
+DC4 = '\x14'
+CAN = '\x18'
+ESC = '\x1b'
+FS  = '\x1c'
+GS  = '\x1d'
+
 # Feed control sequences
-CTL_LF     = '\x0a'               # Print and line feed
-CTL_FF     = '\x0c'               # Form feed
-CTL_CR     = '\x0d'               # Carriage return
-CTL_HT     = '\x09'               # Horizontal tab
-CTL_SET_HT = '\x1b\x44'           # Set horizontal tab positions
-CTL_VT     = '\x1b\x64\x04'       # Vertical tab
+CTL_LF = '\n'             # Print and line feed
+CTL_FF = '\f'             # Form feed
+CTL_CR = '\r'             # Carriage return
+CTL_HT = '\t'             # Horizontal tab
+CTL_SET_HT = ESC + '\x44' # Set horizontal tab positions
+CTL_VT = '\v'             # Vertical tab
+
 # Printer hardware
-HW_INIT    = '\x1b\x40'           # Clear data in buffer and reset modes
-HW_SELECT  = '\x1b\x3d\x01'       # Printer select
-HW_RESET   = '\x1b\x3f\x0a\x00'   # Reset printer hardware
-# Cash Drawer
-CD_KICK_2  = '\x1b\x70\x00'       # Sends a pulse to pin 2 []
-CD_KICK_5  = '\x1b\x70\x01'       # Sends a pulse to pin 5 []
-# Paper
-PAPER_FULL_CUT  = '\x1d\x56\x00'  # Full cut paper
-PAPER_PART_CUT  = '\x1d\x56\x01'  # Partial cut paper
+HW_INIT   = ESC + '@'             # Clear data in buffer and reset modes
+HW_SELECT = ESC + '=\x01'         # Printer select
+
+HW_RESET  = ESC + '\x3f\x0a\x00'  # Reset printer hardware
+                                  # (TODO: Where is this specified?)
+
+# Cash Drawer (ESC p <pin> <on time: 2*ms> <off time: 2*ms>)
+_CASH_DRAWER = lambda m, t1='', t2='': ESC + 'p' + m + t1 + t2
+CD_KICK_2 = _CASH_DRAWER('\x00')  # Sends a pulse to pin 2 []
+CD_KICK_5 = _CASH_DRAWER('\x01')  # Sends a pulse to pin 5 []
+
+# Paper Cutter
+_CUT_PAPER = lambda m: GS + 'V' + m
+PAPER_FULL_CUT = _CUT_PAPER('\x00')  # Full cut paper
+PAPER_PART_CUT = _CUT_PAPER('\x01')  # Partial cut paper
+
 # Text format
-TXT_NORMAL      = '\x1b\x21\x00'  # Normal text
-TXT_2HEIGHT     = '\x1b\x21\x10'  # Double height text
-TXT_2WIDTH      = '\x1b\x21\x20'  # Double width text
-TXT_4SQUARE     = '\x1b\x21\x30'  # Quad area text
-TXT_UNDERL_OFF  = '\x1b\x2d\x00'  # Underline font OFF
-TXT_UNDERL_ON   = '\x1b\x2d\x01'  # Underline font 1-dot ON
-TXT_UNDERL2_ON  = '\x1b\x2d\x02'  # Underline font 2-dot ON
-TXT_BOLD_OFF    = '\x1b\x45\x00'  # Bold font OFF
-TXT_BOLD_ON     = '\x1b\x45\x01'  # Bold font ON
-TXT_FONT_A      = '\x1b\x4d\x00'  # Font type A
-TXT_FONT_B      = '\x1b\x4d\x01'  # Font type B
-TXT_ALIGN_LT    = '\x1b\x61\x00'  # Left justification
-TXT_ALIGN_CT    = '\x1b\x61\x01'  # Centering
-TXT_ALIGN_RT    = '\x1b\x61\x02'  # Right justification
+# TODO: Acquire the "ESC/POS Application Programming Guide for Paper Roll
+#       Printers" and tidy up this stuff too.
+TXT_NORMAL     = ESC + '!\x00'     # Normal text
+TXT_2HEIGHT    = ESC + '!\x10'     # Double height text
+TXT_2WIDTH     = ESC + '!\x20'     # Double width text
+TXT_4SQUARE    = ESC + '!\x30'     # Quad area text
+TXT_UNDERL_OFF = ESC + '\x2d\x00'  # Underline font OFF
+TXT_UNDERL_ON  = ESC + '\x2d\x01'  # Underline font 1-dot ON
+TXT_UNDERL2_ON = ESC + '\x2d\x02'  # Underline font 2-dot ON
+TXT_BOLD_OFF   = ESC + '\x45\x00'  # Bold font OFF
+TXT_BOLD_ON    = ESC + '\x45\x01'  # Bold font ON
+TXT_FONT_A     = ESC + '\x4d\x00'  # Font type A
+TXT_FONT_B     = ESC + '\x4d\x01'  # Font type B
+TXT_ALIGN_LT   = ESC + '\x61\x00'  # Left justification
+TXT_ALIGN_CT   = ESC + '\x61\x01'  # Centering
+TXT_ALIGN_RT   = ESC + '\x61\x02'  # Right justification
+
 # Char code table
-CHARCODE_PC437  = '\x1b\x74\x00'  # USA: Standard Europe
-CHARCODE_JIS    = '\x1b\x74\x01'  # Japanese Katakana
-CHARCODE_PC850  = '\x1b\x74\x02'  # Multilingual
-CHARCODE_PC860  = '\x1b\x74\x03'  # Portuguese
-CHARCODE_PC863  = '\x1b\x74\x04'  # Canadian-French
-CHARCODE_PC865  = '\x1b\x74\x05'  # Nordic
-CHARCODE_WEU    = '\x1b\x74\x06'  # Simplified Kanji, Hirakana
-CHARCODE_GREEK  = '\x1b\x74\x07'  # Simplified Kanji
-CHARCODE_HEBREW = '\x1b\x74\x08'  # Simplified Kanji
-CHARCODE_PC1252 = '\x1b\x74\x11'  # Western European Windows Code Set
-CHARCODE_PC866  = '\x1b\x74\x12'  # Cirillic #2
-CHARCODE_PC852  = '\x1b\x74\x13'  # Latin 2
-CHARCODE_PC858  = '\x1b\x74\x14'  # Euro
-CHARCODE_THAI42 = '\x1b\x74\x15'  # Thai character code 42
-CHARCODE_THAI11 = '\x1b\x74\x16'  # Thai character code 11
-CHARCODE_THAI13 = '\x1b\x74\x17'  # Thai character code 13
-CHARCODE_THAI14 = '\x1b\x74\x18'  # Thai character code 14
-CHARCODE_THAI16 = '\x1b\x74\x19'  # Thai character code 16
-CHARCODE_THAI17 = '\x1b\x74\x1a'  # Thai character code 17
-CHARCODE_THAI18 = '\x1b\x74\x1b'  # Thai character code 18
+CHARCODE_PC437  = ESC + '\x74\x00'  # USA: Standard Europe
+CHARCODE_JIS    = ESC + '\x74\x01'  # Japanese Katakana
+CHARCODE_PC850  = ESC + '\x74\x02'  # Multilingual
+CHARCODE_PC860  = ESC + '\x74\x03'  # Portuguese
+CHARCODE_PC863  = ESC + '\x74\x04'  # Canadian-French
+CHARCODE_PC865  = ESC + '\x74\x05'  # Nordic
+CHARCODE_WEU    = ESC + '\x74\x06'  # Simplified Kanji, Hirakana
+CHARCODE_GREEK  = ESC + '\x74\x07'  # Simplified Kanji
+CHARCODE_HEBREW = ESC + '\x74\x08'  # Simplified Kanji
+CHARCODE_PC1252 = ESC + '\x74\x11'  # Western European Windows Code Set
+CHARCODE_PC866  = ESC + '\x74\x12'  # Cirillic #2
+CHARCODE_PC852  = ESC + '\x74\x13'  # Latin 2
+CHARCODE_PC858  = ESC + '\x74\x14'  # Euro
+CHARCODE_THAI42 = ESC + '\x74\x15'  # Thai character code 42
+CHARCODE_THAI11 = ESC + '\x74\x16'  # Thai character code 11
+CHARCODE_THAI13 = ESC + '\x74\x17'  # Thai character code 13
+CHARCODE_THAI14 = ESC + '\x74\x18'  # Thai character code 14
+CHARCODE_THAI16 = ESC + '\x74\x19'  # Thai character code 16
+CHARCODE_THAI17 = ESC + '\x74\x1a'  # Thai character code 17
+CHARCODE_THAI18 = ESC + '\x74\x1b'  # Thai character code 18
+
 # Barcode format
-BARCODE_TXT_OFF = '\x1d\x48\x00'  # HRI barcode chars OFF
-BARCODE_TXT_ABV = '\x1d\x48\x01'  # HRI barcode chars above
-BARCODE_TXT_BLW = '\x1d\x48\x02'  # HRI barcode chars below
-BARCODE_TXT_BTH = '\x1d\x48\x03'  # HRI barcode chars both above and below
-BARCODE_FONT_A  = '\x1d\x66\x00'  # Font type A for HRI barcode chars
-BARCODE_FONT_B  = '\x1d\x66\x01'  # Font type B for HRI barcode chars
-BARCODE_HEIGHT  = '\x1d\x68\x64'  # Barcode Height [1-255]
-BARCODE_WIDTH   = '\x1d\x77\x03'  # Barcode Width  [2-6]
-BARCODE_UPC_A   = '\x1d\x6b\x00'  # Barcode type UPC-A
-BARCODE_UPC_E   = '\x1d\x6b\x01'  # Barcode type UPC-E
-BARCODE_EAN13   = '\x1d\x6b\x02'  # Barcode type EAN13
-BARCODE_EAN8    = '\x1d\x6b\x03'  # Barcode type EAN8
-BARCODE_CODE39  = '\x1d\x6b\x04'  # Barcode type CODE39
-BARCODE_ITF     = '\x1d\x6b\x05'  # Barcode type ITF
-BARCODE_NW7     = '\x1d\x6b\x06'  # Barcode type NW7
+_SET_BARCODE_TXT_POS = lambda n: GS + 'H' + n
+BARCODE_TXT_OFF = _SET_BARCODE_TXT_POS('\x00')  # HRI barcode chars OFF
+BARCODE_TXT_ABV = _SET_BARCODE_TXT_POS('\x01')  # HRI barcode chars above
+BARCODE_TXT_BLW = _SET_BARCODE_TXT_POS('\x02')  # HRI barcode chars below
+BARCODE_TXT_BTH = _SET_BARCODE_TXT_POS('\x03')  # HRI both above and below
+
+_SET_HRI_FONT = lambda n: GS + 'f' + n
+BARCODE_FONT_A = _SET_HRI_FONT('\x00')  # Font type A for HRI barcode chars
+BARCODE_FONT_B = _SET_HRI_FONT('\x01')  # Font type B for HRI barcode chars
+
+BARCODE_HEIGHT = GS + 'h' + '\x64'  # Barcode Height [1-255]
+BARCODE_WIDTH  = GS + 'w' + '\x03'  # Barcode Width  [2-6]
+
+#NOTE: This isn't actually an ESC/POS command. It's the common prefix to the
+#      two "print bar code" commands:
+#      -  "GS k <type as integer> <data> NUL"
+#      -  "GS k <type as letter> <data length> <data>"
+#      The latter command supports more barcode types
+_SET_BARCODE_TYPE = lambda m: GS + 'k' + m
+BARCODE_UPC_A  = _SET_BARCODE_TYPE('\x00')  # Barcode type UPC-A
+BARCODE_UPC_E  = _SET_BARCODE_TYPE('\x01')  # Barcode type UPC-E
+BARCODE_EAN13  = _SET_BARCODE_TYPE('\x02')  # Barcode type EAN13
+BARCODE_EAN8   = _SET_BARCODE_TYPE('\x03')  # Barcode type EAN8
+BARCODE_CODE39 = _SET_BARCODE_TYPE('\x04')  # Barcode type CODE39
+BARCODE_ITF    = _SET_BARCODE_TYPE('\x05')  # Barcode type ITF
+BARCODE_NW7    = _SET_BARCODE_TYPE('\x06')  # Barcode type NW7
+
 # Image format
-S_RASTER_N      = '\x1d\x76\x30\x00'  # Set raster image normal size
-S_RASTER_2W     = '\x1d\x76\x30\x01'  # Set raster image double width
-S_RASTER_2H     = '\x1d\x76\x30\x02'  # Set raster image double height
-S_RASTER_Q      = '\x1d\x76\x30\x03'  # Set raster image quadruple
+# NOTE: _PRINT_RASTER_IMG is the obsolete ESC/POS "print raster bit image"
+#       command. The constants include a fragment of the data's header.
+_PRINT_RASTER_IMG = lambda data: GS + 'v0' + data
+S_RASTER_N  = _PRINT_RASTER_IMG('\x00')  # Set raster image normal size
+S_RASTER_2W = _PRINT_RASTER_IMG('\x01')  # Set raster image double width
+S_RASTER_2H = _PRINT_RASTER_IMG('\x02')  # Set raster image double height
+S_RASTER_Q  = _PRINT_RASTER_IMG('\x03')  # Set raster image quadruple
+
 # Printing Density
-PD_N50          = '\x1d\x7c\x00'  # Printing Density -50%
-PD_N37          = '\x1d\x7c\x01'  # Printing Density -37.5%
-PD_N25          = '\x1d\x7c\x02'  # Printing Density -25%
-PD_N12          = '\x1d\x7c\x03'  # Printing Density -12.5%
-PD_0            = '\x1d\x7c\x04'  # Printing Density  0%
-PD_P50          = '\x1d\x7c\x08'  # Printing Density +50%
-PD_P37          = '\x1d\x7c\x07'  # Printing Density +37.5%
-PD_P25          = '\x1d\x7c\x06'  # Printing Density +25%
-PD_P12          = '\x1d\x7c\x05'  # Printing Density +12.5%
+PD_N50          = GS + '\x7c\x00'  # Printing Density -50%
+PD_N37          = GS + '\x7c\x01'  # Printing Density -37.5%
+PD_N25          = GS + '\x7c\x02'  # Printing Density -25%
+PD_N12          = GS + '\x7c\x03'  # Printing Density -12.5%
+PD_0            = GS + '\x7c\x04'  # Printing Density  0%
+PD_P50          = GS + '\x7c\x08'  # Printing Density +50%
+PD_P37          = GS + '\x7c\x07'  # Printing Density +37.5%
+PD_P25          = GS + '\x7c\x06'  # Printing Density +25%
+PD_P12          = GS + '\x7c\x05'  # Printing Density +12.5%