# BPM (time service)

BPM is the call sign of the official short-wave time signal service of the People's Republic of China, operated by the Chinese Academy of Sciences, broadcasting from CAS's National Time Service Center in Pucheng County, Shaanxi at 34°56′55.96″N 109°32′34.93″E﻿ / ﻿34.9488778°N 109.5430361°E﻿ / 34.9488778; 109.5430361, roughly 70 km northeast of Lintong, along with NTSC's long-wave time signal BPL on 100 kHz.
BPM is broadcast at 2.5, 5.0, 10.0, and 15.0 MHz, the same frequencies as WWV and WWVH, following the schedule listed below:
| MHz | UTC | CST |
| 2.5 | 7:30-1:00 | 15:30-9:00 |
| 5 | 0:00-24:00 | 0:00-24:00 |
| 10 | 0:00-24:00 | 0:00-24:00 |
| 15 | 1:00-9:00 | 9:00-17:00 |

## Transmission format

BPM transmits different signals on a half-hour schedule, modulated with 1 kHz audio tones to provide second and minute ticks:
BPM transmission schedule :
| Minute | Minute | Duration | Transmission |
| 00 | 30 | 10 | UTC: 10 ms second ticks, 300 ms minute ticks, in advance by 20 ms. BCD time code on 100 Hz sub-carrier. |
| 10 | 40 | 5 | Carrier (no time code) |
| 15 | 45 | 10 | UTC: 10 ms second ticks, 300 ms minute ticks, in advance by 20 ms. BCD time code on 100 Hz sub-carrier. |
| 25 | 55 | 4 | UT1: 100 ms second ticks, 300 ms minute ticks. |
| 29 | 59 | 1 | Station identification: Morse call sign for 40 seconds, then voice announcement "BPM 标准时间标准频率发播台" ("BPM standard time, standard frequency transmission station") twice for 20 seconds. |
BPM is idiosyncratic in that it transmits UT1 time between minutes 25 through to 29 and 55 through to 59, which creates an odd click-beep effect when heard below a stronger time signal station such as WWV especially when UT1 seconds are halfway between UTC seconds, close to a leap-second event.
BPM time code :
| Bit | Weight | Meaning | Ex | Bit | Weight | Meaning | Ex | Bit | Weight | Meaning | Ex |
| :00 | No 125 Hz (minute mark) | No 125 Hz (minute mark) | No 125 Hz (minute mark) | :20 | 1 | Day of month Example: 28 | 0 | :40 | 1 | Year Example: 06 | 0 |
| :01 | 1 | Minutes Example: 23 | 1 | :21 | 2 | Day of month Example: 28 | 0 | :41 | 2 | Year Example: 06 | 1 |
| :02 | 2 | Minutes Example: 23 | 1 | :22 | 4 | Day of month Example: 28 | 0 | :42 | 4 | Year Example: 06 | 1 |
| :03 | 4 | Minutes Example: 23 | 0 | :23 | 8 | Day of month Example: 28 | 1 | :43 | 8 | Year Example: 06 | 0 |
| :04 | 8 | Minutes Example: 23 | 0 | :24 | 0 | Day of month Example: 28 | 0 | :44 | 0 | Year Example: 06 | 0 |
| :05 | 0 | Minutes Example: 23 | 0 | :25 | 10 | Day of month Example: 28 | 0 | :45 | 10 | Year Example: 06 | 0 |
| :06 | 10 | Minutes Example: 23 | 0 | :26 | 20 | Day of month Example: 28 | 1 | :46 | 20 | Year Example: 06 | 0 |
| :07 | 20 | Minutes Example: 23 | 1 | :27 | 0 | Reserved, always 0. | 0 | :47 | 40 | Year Example: 06 | 0 |
| :08 | 40 | Minutes Example: 23 | 0 | :28 | 0 | Reserved, always 0. | 0 | :48 | 80 | Year Example: 06 | 0 |
| :09 | P1 | Marker | M | :29 | P3 | Marker | M | :49 | P5 | Marker | M |
| :10 | 1 | Hours Example: 19 | 1 | :30 | 1 | Month Example: 02 | 0 | :50 | + | DUT1 sign (1=positive) | 1 |
| :11 | 2 | Hours Example: 19 | 0 | :31 | 2 | Month Example: 02 | 1 | :51 | 0.1 | DUT1 magnitude (0 to 0.9 s) DUT1 = UT1−UTC Example: +0.5 s | 1 |
| :12 | 4 | Hours Example: 19 | 0 | :32 | 4 | Month Example: 02 | 0 | :52 | 0.2 | DUT1 magnitude (0 to 0.9 s) DUT1 = UT1−UTC Example: +0.5 s | 0 |
| :13 | 8 | Hours Example: 19 | 1 | :33 | 8 | Month Example: 02 | 0 | :53 | 0.4 | DUT1 magnitude (0 to 0.9 s) DUT1 = UT1−UTC Example: +0.5 s | 1 |
| :14 | 0 | Hours Example: 19 | 0 | :34 | 0 | Month Example: 02 | 0 | :54 | 0.8 | DUT1 magnitude (0 to 0.9 s) DUT1 = UT1−UTC Example: +0.5 s | 0 |
| :15 | 10 | Hours Example: 19 | 1 | :35 | 10 | Month Example: 02 | 0 | :55 | 0 | Reserved, always 0. | 0 |
| :16 | 20 | Hours Example: 19 | 0 | :36 | 0 | Reserved, always 0. | 0 | :56 | 0 | Reserved, always 0. | 0 |
| :17 | 0 | Reserved, always 0. | 0 | :37 | 0 | Reserved, always 0. | 0 | :57 | LS | Leap second | 0 |
| :18 | 0 | Reserved, always 0. | 0 | :38 | 0 | Reserved, always 0. | 0 | :58 | 0 | Reserved, always 0. | 0 |
| :19 | P2 | Marker | M | :39 | P4 | Marker | M | :59 | P0 | Marker | M |