Each 9-1-1 agency has its own Standard Operation Procedures (SOP). Each call taker is to follow this SOP for hang-up calls regardless if the caller is using voice or TTY. It is common practice for call takers to call back on hang-up calls – if there is no response, most of the time they would inform police. Police stations have their own SOPs on how they handle these types of calls. Call takers should be aware that they are to respond in TTY whenever it is silence, open line or the sound of beeping sounds is heard. Even though voice is not heard, call takers are to challenge such calls as a potential TTY call. If TTY calls are hang-up, it is most likely that call takers may not be trained or may be busy with high volume of calls. In that case, this area needs to be evaluated and also policy for processing hang-up calls needs to be reviewed. The document on TTY handling calls can be found in NENA website http://www.nena.org/standards/operations/tty-training-standard. Currently this document is being revised by both NENA and APCO (Association of Public Safety Communication Officials). As soon as it is completed, it will be posted in the website. Please check NENA and APCO websites. In addition, there are several programs called Phone Pal and TTY Pass. The TTY Pass program is a testing program that enable call takers to handle TTY calls as properly, promptly, and reliably as voice calls. Please visit this site, http://www.nena.org/tty-pass for additional information. The Phone Pal program involves people from community to test call on TTY and other aspects as part of routine testing to strengthen the communication skills of call takers and to ensure that their TTYs are working properly. This information can be found in this website http://www.nena.org/standards/operations/tty-phone-pal-program.