Audio transmitters | telephone line

Monitoring of telephone lines:

Monitoring of telephone lines:

These days, not being actual, considering expansion of GSM mobile communication on worldwide basis. If the actual situation requires setting of facilities for monitoring of lines, it belongs to financially bearable, and if it leads to fruition of monitoring, then this sphere is quite well advanced. On the market, these offered products are of quite a high quality, in sufficient variety, of different technical features, but of very different prices, too. Generally, parallel to the telephone line, it’s possible to connect any telephone set, from which we put off the microphone and we can listen.... At present, it’s hardly feasible and also financially expensive  to have somebody  there permanently who would control the possible recording device. Moreover, sometimes it is not possible considering actual conditions. That’s why  the current technique is applied. Before installation of monitoring device on the phone line, it is generally recommended to check, whether  the terminal telephone set is not wireless one and does not transmit on any from pre-defined channels. Then easy choose on scanner or let scan the band and monitoring is finished. For information, in the scheme we show the most usual frequencies of telephones (stationary part, which is more powerful than the mobile part) operating in the Czech Republic and some unnamed neighbouring countries.

Band 30 MHz                                            Band 46 MHz

channel ............... frequency                        channel ............... frequency

1. ................... 30.075  MHz                         1. ................... 46.610  MHz
2. ................... 30.100  MHz                         2. ................... 46.630  MHz
3. ................... 30.125  MHz                         3. ................... 46.670  MHz
4. ................... 30.150  MHz                         4. ................... 46.710  MHz
5. ................... 30.175  MHz                         5. ................... 46.730  MHz
6. ................... 30.200  MHz                         6. ................... 46.770  MHz
7. ................... 30.225  MHz                         7. ................... 46.830  Mhz
8. ................... 30.250  MHz                         8. ................... 46.870  MHz
9. ................... 30.275  MHz                         9. ................... 46.930  MHz

10. ................. 30.300  MHz                         10. ................. 46.970  MHz