While not BSP, and definitely not MilSpec, I like to use Altronix relays (Google "Altronix relay") which are designed for the alarm industry. There is a whole family of relays in 12 and 24 volts, power supplies with or w/o charging capability, and mounting rails and enclosures to make a neat installation.

I have used dial intercom units for controls and have mounted them and these relays in a metal alarm panel box. If you are using a Teltone icm unit, you can use a single code (such as a 5) to operate and latch, and its complementary two-digit code (such as 25) to knock it down.

Or if the device being controlled only needs to be up while the DICM is off-hook (like a paging unit or speaker) you can use the LAMP or other Off Normal lead to hold the relay, so that when you go On Hook, the relay falls.

You can often find Altronix relays on Ebay.

Arthur P. Bloom
"30 years of faithful service...15 years on hold"