Dear John,
Thank you for reaching Small Business Support Community.
According to the USB modems compatibility list below I see only the Pantech UML290 is compatible with the SRP541 running the latest firmware release v1.2.6;
http://www.cisco.com/en/US/docs/voice_ip_comm/unified_communications/srp540_series/modem_comp_matrix/compatiblity_matrix_SRP520-U_and_SRP540_Series_July2013.pdf
And there is already an End of Life announcement for this router that states that after August 5th this year Cisco engineering will no longer develop, repair, maintain, or test the product software.
http://www.cisco.com/en/US/prod/collateral/routers/ps10907/ps10500/end_of_life_notice_c51-728170.html
I do not think there is going to be a newer firmware release within this coming week. Please let me know if there is anything else I may assist you with.
Kind regards,
Jeffrey Rodriguez S. .:|:.:|:.
Cisco Customer Support Engineer
*Please rate the Post so other will know when an answer has been found.
Jeffrey Rodriguez S. .:|:.:|:.
Cisco Customer Support Engineer
*Please rate the Post so other will know when an answer has been found.