# 2 Meter Transceiver Information
 PTT OFF 4.97 V ON 0.98 V
Note: No current measurement made. ---- Yeasu FM-Transceiver Model FT-1500M
Button SW1 (V) SW2 (V)
no button 4.95 4.95
1 0.11 1.06
2 0.11 1.96
3 0.11 2.94
A 0.11 3.98
4 0.99 1.06
5 0.99 1.96
6 0.99 2.94
B 0.99 3.98
7 1.98 1.06
8 1.98 1.96
9 1.98 2.94
C 1.98 3.98
* 2.97 1.06
0 2.97 1.96
# 2.97 2.94
D 2.97 3.98
P1 3.91 1.06
P2 3.91 1.96
P3 3.91 2.94
P4 3.91 3.98
UP 1.16 0.22
DWN 2.11 0.22
So it looks like SW1, SW2 can take on 6 distinct voltage levels:
 SW1 SW2 0.11 0.99,1.16 1.98, 2.11 2.97 3.91 4.95 0.22 1.06 1.96 2.94 3.98 4.95
Note that we're considering any voltage change of > 0.25 V to be significantly different; this implied that SW1's 0.99V and 1.16V are meant to be the same level, even though they're slightly differnet voltages (off by 0.17V)... but we're guessing the radio has fairly large tolerances to take care of component drift, etc. In fact, it looks as if they could set their comparators 0.5V, 1.5V, 2.5V, 3.5V, 4.5V and they'd get a ~ 0.5 V minimum of room for noise and spurious signals.
 1209 Hz 1336 Hz 1477 Hz 1633 Hz 1 2 3 A 4 5 6 B 7 8 9 C * 0 # D