Could you suggest me which IOS I can use to upgrade my CISCO 3620 with VOIP capabilty ?

Now the router is running with c3620-is-mz.122-13b.bin, I tried to load  c3620-jsx-mz.122-40.bin, but after the reload I got a memory error, unfortunatly I couldn't same the error message 

System flash directory:
File  Length   Name/status
  1   11199660  c3620-is-mz.122-13b.bin
  2   13310136  c3620-jsx-mz.122-40.bin
[24509924 bytes used, 8520220 available, 33030144 total]
32768K bytes of processor board System flash (Read/Write)

XXXXXXX#show mem
                Head    Total(b)     Used(b)     Free(b)   Lowest(b)  Largest(b)
Processor   61D42320    31186144    12413784    18772360    17918756    17610592
      I/O    3B00000     5242880     2945004     2297876     2220656     2295900

Actual IOS

XXXXXXX#show ver
Cisco Internetwork Operating System Software
IOS (tm) 3600 Software (C3620-IS-M), Version 12.2(13b), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2003 by cisco Systems, Inc.
Compiled Fri 21-Feb-03 09:52 by pwade
Image text-base: 0x60008930, data-base: 0x61112000

ROM: System Bootstrap, Version 11.1(20)AA2, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1)

XXXXXXX uptime is 3 weeks, 4 days, 3 hours, 51 minutes
System returned to ROM by power-on
System restarted at 09:11:24 CET-1CEST-2 Tue Oct 27 2009
System image file is "flash:c3620-is-mz.122-13b.bin"

cisco 3620 (R4700) processor (revision 0x81) with 60416K/5120K bytes of memory.
Processor board ID 18119770
R4700 CPU at 80Mhz, Implementation 33, Rev 1.0
Channelized E1, Version 1.0.
Bridging software.
X.25 software, Version 3.0.0.
SuperLAT software (copyright 1990 by Meridian Technology Corp).
Primary Rate ISDN software, Version 1.1.
1 Ethernet/IEEE 802.3 interface(s)
62 Serial network interface(s)
2 Channelized E1/PRI port(s)
DRAM configuration is 32 bits wide with parity disabled.
29K bytes of non-volatile configuration memory.
32768K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

Thanks